Methods and systems for engine-off disengagement of a vehicle park state

ABSTRACT

Methods and systems are provided for launching a vehicle in an electric-only mode of operation. In one example, a driveline operating method comprises engaging a parking pawl to an output shaft of a dual clutch transmission in response to a request to engine a vehicle into a parked state, and disengaging the parking pawl via rotating an engine via an integrated starter/generator in response to a request to propel the vehicle solely via power of an electric machine positioned downstream of the dual clutch transmission. In this way, the vehicle may be launched in the electric-only mode without activating the engine in a fueled mode of operation and then deactivating the engine, which may increase vehicle operator satisfaction and which may improve fuel economy.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional PatentApplication No. 62/415,392 entitled “Methods and System for a HybridVehicle,” filed on Oct. 31, 2016. The entire contents of theabove-referenced application are hereby incorporated by reference intheir entirety for all purposes.

FIELD

The present description relates generally to methods and systems forcontrolling a driveline of a hybrid vehicle. The methods and systems maybe particularly useful for hybrid vehicles that include a dual clutchtransmission.

BACKGROUND/SUMMARY

A hybrid vehicle may be propelled by an engine and/or an electricmachine. In such a vehicle, there can be powertrain modes that enablethe vehicle to be propelled using only the electric machine with thetransmission input clutch(es) open, allowing the engine to bestationary. Such vehicles may in some examples include a park-pawl,comprising a device fitted to the vehicle's transmission in order tolock up the transmission. Specifically, the parking pawl locks thetransmission's output shaft by engaging a pawl or pin that engages anotched wheel on the output shaft, thus stopping it and the drivenwheels from rotating. To disengage the parking pawl typically requiresengine operation. However, for a hybrid vehicle that offers functionssuch as silent drive away using an electric-only mode of operation, itmay not be desirable to start the engine to release park, and then turnthe engine off again. Such actions may be inefficient, and may becounterintuitive to the vehicle operator.

The inventors have recognized the above-mentioned issues, and havedeveloped systems and methods to at least partially address them. In oneexample, a method comprises engaging a parking pawl to an output shaftof a dual clutch transmission in response to a request to enter avehicle into a parked state; and disengaging the parking pawl viarotating an engine via an integrated starter/generator in response to arequest to propel the vehicle solely via power of an electric machinepositioned downstream of the dual clutch transmission.

In one example, such a method includes ceasing engine rotation inresponse to an indication that the parking pawl is released. In thisway, a hybrid vehicle may be enabled to launch the vehicle in anelectric-only mode of operation, without undesirably activating theengine in a fueled mode of operation, and then deactivating the engine.By avoiding fueled engine operation to release the parking pawl, fuelefficiency may be increased, undesired emissions may be reduced, andcustomer satisfaction may be improved.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a hybrid vehicle driveline;

FIG. 1B is a sketch of an engine of the hybrid vehicle driveline;

FIG. 2 is a schematic diagram of a fuel vapor management system for ahybrid vehicle;

FIG. 3 is a schematic diagram of the hybrid vehicle driveline includingcontrollers of various driveline components;

FIG. 4 is a schematic diagram of a dual clutch transmission located inthe hybrid vehicle driveline;

FIG. 5 is a flowchart of a method for engaging a dual clutchtransmission in a park state;

FIG. 6 is a simulated sequence for engaging a dual clutch transmissionin a park state;

FIG. 7 is a flowchart of a method for operating a parking pawl of a dualclutch transmission;

FIG. 8 is a simulated sequence for engaging and releasing a parking pawlof a dual clutch transmission;

FIG. 9 is a flowchart of a method to control a hybrid drivelineresponsive to vehicle stability;

FIG. 10 is a simulated sequence for operating a hybrid drivelineresponsive to vehicle stability;

FIGS. 11 and 12 are flowcharts for a method to adapt clutches of a dualclutch transmission operating in a driveline of a hybrid vehicle;

FIG. 13 is a block diagram showing how a clutch is engaged ordisengaged;

FIGS. 14A and 14B are simulated sequences for adapting clutches of adual clutch transmission of a hybrid vehicle driveline;

FIG. 15 is a flowchart of a method for shifting a dual clutchtransmission of a hybrid vehicle;

FIGS. 16A-16D are block diagrams of ways to determine compensationtorque for shifting a dual clutch transmission of a hybrid vehicle whilean engine is stopped and not combusting air and fuel;

FIGS. 17A and 17B are simulated sequences for shifting a dual clutchtransmission of a hybrid vehicle;

FIGS. 18A and 18B show a flowchart of a method of starting an engine andengaging the engine to a dual clutch transmission; and

FIGS. 19A and 19B are simulated engine starting sequences.

DETAILED DESCRIPTION

The following description relates to systems and methods for operating adriveline of a hybrid vehicle. FIGS. 1A-4 show an example hybrid vehiclesystem that includes a driveline with a motor, an integratedstarter/generator, a dual clutch transmission, and an electric machinethat is positioned downstream of the dual clutch transmission. FIGS. 5-8describe and show operation of ways to engage and disengage a park statein the dual clutch transmission. FIGS. 9 and 10 describe ways ofcontrolling the hybrid vehicle driveline that may improve vehiclestability. Clutches of the dual clutch transmission may be adapted andused during shifting of the dual clutch transmission as described inFIGS. 11-17B. An engine of a hybrid vehicle may be started and engagedto other components of the hybrid vehicle driveline as described inFIGS. 18A-19B.

FIG. 1A illustrates an example vehicle propulsion system 100 for vehicle121. Vehicle propulsion system 100 includes at least two power sourcesincluding an internal combustion engine 110 and an electric machine 120.Electric machine 120 may be configured to utilize or consume a differentenergy source than engine 110. For example, engine 110 may consumeliquid fuel (e.g. gasoline) to produce an engine output while electricmachine 120 may consume electrical energy to produce an electric machineoutput. As such, a vehicle with propulsion system 100 may be referred toas a hybrid electric vehicle (HEV). Throughout the description of FIG.1A, mechanical connections between various components is illustrated assolid lines, whereas electrical connections between various componentsare illustrated as dashed lines.

Vehicle propulsion system 100 has a front axle (not shown) and a rearaxle 122. In some examples, rear axle may comprise two half shafts, forexample first half shaft 122 a, and second half shaft 122 b. Vehiclepropulsion system 100 further has front wheels 130 and rear wheels 131.The rear axle 122 is coupled to electric machine 120 and transmission125, via which the rear axle 122 may be driven. The rear axle 122 may bedriven either purely electrically and exclusively via electric machine120 (e.g., electric only drive or propulsion mode, engine is notcombusting air and fuel or rotating), in a hybrid fashion via electricmachine 120 and engine 110 (e.g., parallel mode), or exclusively viaengine 110 (e.g., engine only propulsion mode), in a purely combustionengine-operated fashion. Rear drive unit 136 may transfer power fromengine 110 or electric machine 120, to axle 122, resulting in rotationof drive wheels 131. Rear drive unit 136 may include a gear set and oneor more clutches to decouple transmission 125 and electric machine 120from wheels 131.

A transmission 125 is illustrated in FIG. 1A as connected between engine110, and electric machine 120 assigned to rear axle 122. In one example,transmission 125 is a dual clutch transmission (DCT). In an examplewherein transmission 125 is a DCT, DCT may include a first clutch 126, asecond clutch 127, and a gear box 128. DCT 125 outputs torque to driveshaft 129 to supply torque to wheels 131. As will be discussed infurther detail below with regard to FIG. 3, transmission 125 may shiftgears by selectively opening and closing first clutch 126 and secondclutch 127.

Electric machine 120 may receive electrical power from onboard energystorage device 132. Furthermore, electric machine 120 may provide agenerator function to convert engine output or the vehicle's kineticenergy into electrical energy, where the electrical energy may be storedat energy storage device 132 for later use by the electric machine 120or integrated starter/generator 142. A first inverter system controller(ISC1) 134 may convert alternating current generated by electric machine120 to direct current for storage at the energy storage device 132 andvice versa.

In some examples, energy storage device 132 may be configured to storeelectrical energy that may be supplied to other electrical loadsresiding on-board the vehicle (other than the motor), including cabinheating and air conditioning, engine starting, headlights, cabin audioand video systems, etc. As a non-limiting example, energy storage device150 may include one or more batteries and/or capacitors.

Control system 14 may communicate with one or more of engine 110,electric machine 120, energy storage device 132, integratedstarter/generator 142, transmission 125, etc. Control system 14 mayreceive sensory feedback information from one or more of engine 110,electric machine 120, energy storage device 132, integratedstarter/generator 142, transmission 125, etc. Further, control system 14may send control signals to one or more of engine 110, electric machine120, energy storage device 132, transmission 125, etc., responsive tothis sensory feedback. Control system 14 may receive an indication of anoperator requested output of the vehicle propulsion system from a humanoperator 102, or an autonomous controller. For example, control system14 may receive sensory feedback from pedal position sensor 194 whichcommunicates with pedal 192. Pedal 192 may refer schematically to anaccelerator pedal. Similarly, control system 14 may receive anindication of an operator requested vehicle braking via a human operator102, or an autonomous controller. For example, control system 14 mayreceive sensory feedback from pedal position sensor 157 whichcommunicates with brake pedal 156.

Energy storage device 132 may periodically receive electrical energyfrom a power source 180 (e.g., a stationary power grid) residingexternal to the vehicle (e.g., not part of the vehicle) as indicated byarrow 184. As a non-limiting example, vehicle propulsion system 100 maybe configured as a plug-in hybrid electric vehicle (HEV), wherebyelectrical energy may be supplied to energy storage device 132 frompower source 180 via an electrical energy transmission cable 182. Duringa recharging operation of energy storage device 132 from power source180, electrical transmission cable 182 may electrically couple energystorage device 132 and power source 180. In some examples, power source180 may be connected at inlet port 150. Furthermore, in some examples, acharge status indicator 151 may display a charge status of energystorage device 132.

In some examples, electrical energy from power source 180 may bereceived by charger 152. For example, charger 152 may convertalternating current from power source 180 to direct current (DC), forstorage at energy storage device 132. Furthermore, a DC/DC converter 153may convert a source of direct current from charger 152 from one voltageto another voltage. In other words, DC/DC converter 153 may act as atype of electric power converter.

While the vehicle propulsion system is operated to propel the vehicle,electrical transmission cable 182 may be disconnected between powersource 180 and energy storage device 132. Control system 14 may identifyand/or control the amount of electrical energy stored at the energystorage device, which may be referred to as the state of charge (SOC).

In other examples, electrical transmission cable 182 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 150 from power source 180. For example, energy storage device 150may receive electrical energy from power source 180 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 132 from a power source that doesnot comprise part of the vehicle. In this way, electric machine 120 maypropel the vehicle by utilizing an energy source other than the fuelutilized by engine 110.

Electric energy storage device 132 includes an electric energy storagedevice controller 139 and a power distribution module 138. Electricenergy storage device controller 139 may provide charge balancingbetween energy storage element (e.g., battery cells) and communicationwith other vehicle controllers (e.g., controller 12). Power distributionmodule 138 controls flow of power into and out of electric energystorage device 132.

Vehicle propulsion system 100 may also include an ambienttemperature/humidity sensor 198, and sensors dedicated to indicating theoccupancy-state of the vehicle, for example onboard cameras 105, seatload cells 107, and door sensing technology 108. Vehicle system 100 mayalso include inertial sensors 199. Inertial sensors 199 may comprise oneor more of the following: longitudinal, latitudinal, vertical, yaw,roll, and pitch sensors (e.g., accelerometers). Axes of yaw, pitch,roll, lateral acceleration, and longitudinal acceleration are asindicated. As one example, inertial sensors 199 may couple to thevehicle's restraint control module (RCM) (not shown), the RCM comprisinga subsystem of control system 14. The control system may adjust engineoutput and/or the wheel brakes to increase vehicle stability in responseto sensor(s) 199. In another example, the control system may adjust anactive suspension system 111 responsive to input from inertial sensors199. Active suspension system 111 may comprise an active suspensionsystem having hydraulic, electrical, and/or mechanical devices, as wellas active suspension systems that control the vehicle height on anindividual corner basis (e.g., four corner independently controlledvehicle heights), on an axle-by-axle basis (e.g., front axle and rearaxle vehicle heights), or a single vehicle height for the entirevehicle. Data from inertial sensor 199 may also be communicated tocontroller 12, or alternatively, sensors 199 may be electrically coupledto controller 12.

One or more tire pressure monitoring sensors (TPMS) may be coupled toone or more tires of wheels in the vehicle. For example, FIG. 1A shows atire pressure sensor 197 coupled to wheel 131 and configured to monitora pressure in a tire of wheel 131. While not explicitly illustrated, itmay be understood that each of the four tires indicated in FIG. 1A mayinclude one or more tire pressure sensor(s) 197. Furthermore, in someexamples, vehicle propulsion system 100 may include a pneumatic controlunit 123. Pneumatic control unit may receive information regarding tirepressure from tire pressure sensor(s) 197, and send said tire pressureinformation to control system 14. Based on said tire pressureinformation, control system 14 may command pneumatic control unit 123 toinflate or deflate tire(s) of the vehicle wheels. While not explicitlyillustrated, it may be understood that pneumatic control unit 123 may beused to inflate or deflate tires associated with any of the four wheelsillustrated in FIG. 1A. For example, responsive to an indication of atire pressure decrease, control system 14 may command pneumatic controlsystem unit 123 to inflate one or more tire(s). Alternatively,responsive to an indication of a tire pressure increase, control system14 may command pneumatic control system unit 123 to deflate tire(s) oneor more tires. In both examples, pneumatic control system unit 123 maybe used to inflate or deflate tires to an optimal tire pressure ratingfor said tires, which may prolong tire life.

One or more wheel speed sensors (WSS) 195 may be coupled to one or morewheels of vehicle propulsion system 100. The wheel speed sensors maydetect rotational speed of each wheel. Such an example of a WSS mayinclude a permanent magnet type of sensor.

Vehicle propulsion system 100 may further include an accelerometer 20.Vehicle propulsion system 100 may further include an inclinometer 21.

Vehicle propulsion system 100 may further include a starter 140. Starter140 may comprise an electric motor, hydraulic motor, etc., and may beused to rotate engine 110 so as to initiate engine 110 operation underits own power.

Vehicle propulsion system 100 may further include a brake system controlmodule (BSCM) 141. In some examples, BSCM 141 may comprise an anti-lockbraking system or anti-skid braking system, such that wheels (e.g. 130,131) may maintain tractive contact with the road surface according todriver inputs while braking, which may thus prevent the wheels fromlocking up, to prevent skidding. In some examples, BSCM may receiveinput from wheel speed sensors 195.

Vehicle propulsion system 100 may further include a belt integratedstarter generator (BISG) 142. BISG may produce electric power when theengine 110 is in operation, where the electrical power produced may beused to supply electric devices and/or to charge the onboard storagedevice 132. As indicated in FIG. 1A, a second inverter system controller(ISC2) 143 may receive alternating current from BISG 142, and mayconvert alternating current generated by BISG 142 to direct current forstorage at energy storage device 132. Integrated starter/generator 142may also provide torque to engine 110 during engine starting or otherconditions to supplement engine torque.

Vehicle propulsion system 100 may further include a power distributionbox (PDB) 144. PDB 144 may be used for routing electrical powerthroughout various circuits and accessories in the vehicle's electricalsystem.

Vehicle propulsion system 100 may further include a high current fusebox (HCFB) 145, and may comprise a variety of fuses (not shown) used toprotect the wiring and electrical components of vehicle propulsionsystem 100.

Vehicle propulsion system 100 may further include a motor electronicscoolant pump (MECP) 146. MECP 146 may be used to circulate coolant todiffuse heat generated by at least electric machine 120 of vehiclepropulsion system 100, and the electronics system. MECP may receiveelectrical power from onboard energy storage device 132, as an example.

Controller 12 may comprise a portion of a control system 14. In someexamples, controller 12. Control system 14 is shown receivinginformation from a plurality of sensors 16 (various examples of whichare described herein) and sending control signals to a plurality ofactuators 81 (various examples of which are described herein). As oneexample, sensors 16 may include tire pressure sensor(s) 197, wheel speedsensor(s) 195, ambient temperature/humidity sensor 198, onboard cameras105, seat load cells 107, door sensing technology 108, inertial sensors199, etc. In some examples, sensors associated with engine 110,transmission 125, electric machine 120, etc., may communicateinformation to controller 12, regarding various states of engine,transmission, and motor operation, as will be discussed in furtherdetail with regard to FIG. 1B, FIG. 3 and FIG. 4.

Vehicle propulsion system 100 may further include a positive temperaturecoefficient (PTC) heater 148. As an example, PTC heater 148 may comprisea ceramic material such that when resistance is low, the ceramicmaterial may accept a large amount of current, which may result in arapid warming of the ceramic element. However, as the element warms andreaches a threshold temperature, the resistance may become very large,and as such, may not continue to produce much heat. As such, PTC heater148 may be self-regulating, and may have a good degree of protectionfrom overheating.

Vehicle propulsion system 100 may further include an air conditioningcompressor module 149, for controlling an electric air conditioningcompressor (not shown).

Vehicle propulsion system 100 may further include a vehicle audiblesounder for pedestrians (VASP) 154. For example, VASP 154 may beconfigured to produce audible sounds via sounders 155. In some examples,audible sounds produced via VASP 154 communicating with sounders 155 maybe activated responsive to a vehicle operator triggering the sound, orautomatically, responsive to engine speed below a threshold or detectionof a pedestrian.

Vehicle propulsion system 100 may also include an on-board navigationsystem 17 (for example, a Global Positioning System) on dashboard 19that an operator of the vehicle may interact with. The navigation system17 may include one or more location sensors for assisting in estimatinga location (e.g., geographical coordinates) of the vehicle. For example,on-board navigation system 17 may receive signals from GPS satellites(not shown), and from the signal identify the geographical location ofthe vehicle. In some examples, the geographical location coordinates maybe communicated to controller 12.

Dashboard 19 may further include a display system 18 configured todisplay information to the vehicle operator. Display system 18 maycomprise, as a non-limiting example, a touchscreen, or human machineinterface (HMI), display which enables the vehicle operator to viewgraphical information as well as input commands. In some examples,display system 18 may be connected wirelessly to the internet (notshown) via controller (e.g. 12). As such, in some examples, the vehicleoperator may communicate via display system 18 with an internet site orsoftware application (app).

Dashboard 19 may further include an operator interface 15 via which thevehicle operator may adjust the operating status of the vehicle.Specifically, the operator interface 15 may be configured to initiateand/or terminate operation of the vehicle driveline (e.g., engine 110,BISG 142, DCT 125, and electric machine 120) based on an operator input.Various examples of the operator ignition interface 15 may includeinterfaces that require a physical apparatus, such as an active key,that may be inserted into the operator ignition interface 15 to startthe engine 110 and turn on the vehicle, or may be removed to shut downthe engine 110 and turn off the vehicle. Other examples may include apassive key that is communicatively coupled to the operator ignitioninterface 15. The passive key may be configured as an electronic key fobor a smart key that does not have to be inserted or removed from theignition interface 15 to operate the vehicle engine 10. Rather, thepassive key may need to be located inside or proximate to the vehicle(e.g., within a threshold distance of the vehicle). Still other examplesmay additionally or optionally use a start/stop button that is manuallypressed by the operator to start or shut down the engine 110 and turnthe vehicle on or off. In other examples, a remote engine start may beinitiated remote computing device (not shown), for example a cellulartelephone, or smartphone-based system where a user's cellular telephonesends data to a server and the server communicates with the vehiclecontroller 12 to start the engine.

Referring to FIG. 1B, a detailed view of internal combustion engine 110,comprising a plurality of cylinders, one cylinder of which is shown inFIG. 1B, is shown. Engine 110 is controlled by electronic enginecontroller 111B. Engine 110 includes combustion chamber 30B and cylinderwalls 32B with piston 36B positioned therein and connected to crankshaft40B. Combustion chamber 30B is shown communicating with intake manifold44B and exhaust manifold 48B via respective intake valve 52B and exhaustvalve 54B. Each intake and exhaust valve may be operated by an intakecam 51B and an exhaust cam 53B. The position of intake cam 51B may bedetermined by intake cam sensor 55B. The position of exhaust cam 53B maybe determined by exhaust cam sensor 57B. Intake cam 51B and exhaust cam53B may be moved relative to crankshaft 40B. Intake valves may bedeactivated and held in a closed state via intake valve deactivatingmechanism 59B. Exhaust valves may be deactivated and held in a closedstate via exhaust valve deactivating mechanism 58B.

Fuel injector 66B is shown positioned to inject fuel directly intocylinder 30B, which is known to those skilled in the art as directinjection. Alternatively, fuel may be injected to an intake port, whichis known to those skilled in the art as port injection. Fuel injector66B delivers liquid fuel in proportion to the pulse width of signal fromengine controller 111B. Fuel is delivered to fuel injector 66B by a fuelsystem 175B, which includes a tank and pump. In addition, intakemanifold 44B is shown communicating with optional electronic throttle62B (e.g., a butterfly valve) which adjusts a position of throttle plate64B to control air flow from air filter 43B and air intake 42B to intakemanifold 44B. Throttle 62B regulates air flow from air filter 43B inengine air intake 42B to intake manifold 44B. In some examples, throttle62B and throttle plate 64B may be positioned between intake valve 52Band intake manifold 44B such that throttle 62B is a port throttle.

Distributorless ignition system 88B provides an ignition spark tocombustion chamber 30B via spark plug 92B in response to enginecontroller 111B. Universal Exhaust Gas Oxygen (UEGO) sensor 126B isshown coupled to exhaust manifold 48B upstream of catalytic converter70B in a direction of exhaust flow. Alternatively, a two-state exhaustgas oxygen sensor may be substituted for UEGO sensor 126B.

Converter 70B can include multiple catalyst bricks, in one example. Inanother example, multiple emission control devices, each with multiplebricks, can be used. Converter 70B can be a three-way type catalyst inone example.

Engine controller 111B is shown in FIG. 1B as a conventionalmicrocomputer including: microprocessor unit 102B, input/output ports104B, read-only memory 106B (e.g., non-transitory memory), random accessmemory 108B, keep alive memory 110B, and a conventional data bus. Othercontrollers mentioned herein may have a similar processor and memoryconfiguration. Engine controller 111B is shown receiving various signalsfrom sensors coupled to engine 110, in addition to those signalspreviously discussed, including: engine coolant temperature (ECT) fromtemperature sensor 112B coupled to cooling sleeve 114B; a measurement ofengine manifold pressure (MAP) from pressure sensor 122B coupled tointake manifold 44B; an engine position sensor from a Hall effect sensor118B sensing crankshaft 40B position; a measurement of air mass enteringthe engine from sensor 120B; and a measurement of throttle position fromsensor 58B. Barometric pressure may also be sensed (sensor not shown)for processing by engine controller 111B. In a preferred aspect of thepresent description, engine position sensor 118B produces apredetermined number of equally spaced pulses every revolution of thecrankshaft from which engine speed (RPM) can be determined. Enginecontroller 111B may receive input from human/machine interface 115B(e.g., pushbutton or touch screen display).

During operation, each cylinder within engine 110 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54B closes and intake valve 52B opens. Airis introduced into combustion chamber 30B via intake manifold 44B, andpiston 36B moves to the bottom of the cylinder so as to increase thevolume within combustion chamber 30B. The position at which piston 36Bis near the bottom of the cylinder and at the end of its stroke (e.g.when combustion chamber 30B is at its largest volume) is typicallyreferred to by those of skill in the art as bottom dead center (BDC).During the compression stroke, intake valve 52B and exhaust valve 54Bare closed. Piston 36B moves toward the cylinder head so as to compressthe air within combustion chamber 30B. The point at which piston 36B isat the end of its stroke and closest to the cylinder head (e.g. whencombustion chamber 30B is at its smallest volume) is typically referredto by those of skill in the art as top dead center (TDC). In a processhereinafter referred to as injection, fuel is introduced into thecombustion chamber. In a process hereinafter referred to as ignition,the injected fuel is ignited by known ignition means such as spark plug92B, resulting in combustion. During the expansion stroke, the expandinggases push piston 36B back to BDC. Crankshaft 40B converts pistonmovement into a rotational torque of the rotary shaft. Finally, duringthe exhaust stroke, the exhaust valve 54B opens to release the combustedair-fuel mixture to exhaust manifold 48B and the piston returns to TDC.Note that the above is shown merely as an example, and that intake andexhaust valve opening and/or closing timings may vary, such as toprovide positive or negative valve overlap, late intake valve closing,or various other examples.

FIG. 2 shows a schematic depiction of a vehicle system 206. It may beappreciated that vehicle system 206 may comprise vehicle propulsionsystem 100 depicted at FIG. 1A. The vehicle system 206 includes anengine system 208 coupled to an emissions control system 251 and a fuelsystem 218. Emission control system 251 includes a fuel vapor containeror canister 222 which may be used to capture and store fuel vapors. Insome examples, vehicle system 206 may be a hybrid electric vehiclesystem, such as vehicle propulsion system 100 illustrated at FIG. 1A.

The engine system 208 may include an engine 110 having a plurality ofcylinders 230. The engine 110 includes an engine air intake 223 and anengine exhaust 225. The engine air intake 223 includes a throttle 62B influidic communication with engine intake manifold 44B via an intakepassage 42B. Further, engine air intake 223 may include an air box andfilter (not shown) positioned upstream of throttle 62B. The engineexhaust system 225 includes an exhaust manifold 48B leading to anexhaust passage 235 that routes exhaust gas to the atmosphere. Theengine exhaust system 225 may include one or more exhaust catalyst 70B,which may be mounted in a close-coupled position in the exhaust. One ormore emission control devices may include a three-way catalyst, lean NOxtrap, diesel particulate filter, oxidation catalyst, etc. It will beappreciated that other components may be included in the engine such asa variety of valves and sensors.

Fuel system 218 may include a fuel tank 220 coupled to a fuel pumpsystem 221. The fuel pump system 221 may include one or more pumps forpressurizing fuel delivered to the injectors of engine 110, such as theexample injector 66B shown. While only a single injector 66B is shown,additional injectors are provided for each cylinder. It will beappreciated that fuel system 218 may be a return-less fuel system, areturn fuel system, or various other types of fuel system. Fuel tank 220may hold a plurality of fuel blends, including fuel with a range ofalcohol concentrations, such as various gasoline-ethanol blends,including E10, E85, gasoline, etc., and combinations thereof. A fuellevel sensor 234 located in fuel tank 220 may provide an indication ofthe fuel level (“Fuel Level Input”) to controller 212. As depicted, fuellevel sensor 234 may comprise a float connected to a variable resistor.Alternatively, other types of fuel level sensors may be used.

Vapors generated in fuel system 218 may be routed to an evaporativeemissions control system 251 which includes a fuel vapor canister 222via vapor recovery line 231, before being purged to the engine airintake 223. Vapor recovery line 231 may be coupled to fuel tank 220 viaone or more conduits and may include one or more valves for isolatingthe fuel tank during certain conditions. For example, vapor recoveryline 231 may be coupled to fuel tank 220 via one or more or acombination of conduits 271, 273, and 275.

Further, in some examples, one or more fuel tank vent valves may bepositioned in conduits 271, 273, or 275. Among other functions, fueltank vent valves may allow a fuel vapor canister of the emissionscontrol system to be maintained at a low pressure or vacuum withoutincreasing the fuel evaporation rate from the tank (which wouldotherwise occur if the fuel tank pressure were lowered). For example,conduit 271 may include a grade vent valve (GVV) 287, conduit 273 mayinclude a fill limit venting valve (FLVV) 285, and conduit 275 mayinclude a grade vent valve (GVV) 283. Further, in some examples,recovery line 231 may be coupled to a fuel filler system 219. In someexamples, fuel filler system may include a fuel cap 205 for sealing offthe fuel filler system from the atmosphere. Refueling system 219 iscoupled to fuel tank 220 via a fuel filler pipe or neck 211.

Further, refueling system 219 may include refueling lock 245. In someexamples, refueling lock 245 may be a fuel cap locking mechanism. Thefuel cap locking mechanism may be configured to automatically lock thefuel cap in a closed position so that the fuel cap cannot be opened. Forexample, the fuel cap 205 may remain locked via refueling lock 245 whilepressure or vacuum in the fuel tank is greater than a threshold. Inresponse to a refuel request, e.g., a vehicle operator initiatedrequest, the fuel tank may be depressurized and the fuel cap unlockedafter the pressure or vacuum in the fuel tank falls below a threshold. Afuel cap locking mechanism may be a latch or clutch, which, whenengaged, prevents the removal of the fuel cap. The latch or clutch maybe electrically locked, for example, by a solenoid, or may bemechanically locked, for example, by a pressure diaphragm.

In some examples, refueling lock 245 may be a filler pipe valve locatedat a mouth of fuel filler pipe 211. In such examples, refueling lock 245may not prevent the removal of fuel cap 205. Rather, refueling lock 245may prevent the insertion of a refueling pump into fuel filler pipe 211.The filler pipe valve may be electrically locked, for example by asolenoid, or mechanically locked, for example by a pressure diaphragm.

In some examples, refueling lock 245 may be a refueling door lock, suchas a latch or a clutch which locks a refueling door located in a bodypanel of the vehicle. The refueling door lock may be electricallylocked, for example by a solenoid, or mechanically locked, for exampleby a pressure diaphragm.

In examples where refueling lock 245 is locked using an electricalmechanism, refueling lock 245 may be unlocked by commands fromcontroller 212, for example, when a fuel tank pressure decreases below apressure threshold. In examples where refueling lock 245 is locked usinga mechanical mechanism, refueling lock 245 may be unlocked via apressure gradient, for example, when a fuel tank pressure decreases toatmospheric pressure.

Emissions control system 251 may include one or more emissions controldevices, such as one or more fuel vapor canisters 222 filled with anappropriate adsorbent 286 b, the canisters are configured to temporarilytrap fuel vapors (including vaporized hydrocarbons) during fuel tankrefilling operations and “running loss” (that is, fuel vaporized duringvehicle operation). In one example, the adsorbent 286 b used isactivated charcoal. Emissions control system 251 may further include acanister ventilation path or vent line 227 which may route gases out ofthe canister 222 to the atmosphere when storing, or trapping, fuelvapors from fuel system 218.

Canister 222 may include a buffer 222 a (or buffer region), each of thecanister and the buffer comprising the adsorbent. As shown, the volumeof buffer 222 a may be smaller than (e.g., a fraction of) the volume ofcanister 222. The adsorbent 286 a in the buffer 222 a may be same as, ordifferent from, the adsorbent in the canister (e.g., both may includecharcoal). Buffer 222 a may be positioned within canister 222 such thatduring canister loading, fuel tank vapors are first adsorbed within thebuffer, and then when the buffer is saturated, further fuel tank vaporsare adsorbed in the canister. In comparison, during canister purging,fuel vapors are first desorbed from the canister (e.g., to a thresholdamount) before being desorbed from the buffer. In other words, loadingand unloading of the buffer is not linear with the loading and unloadingof the canister. As such, the effect of the canister buffer is to dampenany fuel vapor spikes flowing from the fuel tank to the canister,thereby reducing the possibility of any fuel vapor spikes going to theengine. One or more temperature sensors 232 may be coupled to and/orwithin canister 222. As fuel vapor is adsorbed by the adsorbent in thecanister, heat is generated (heat of adsorption). Likewise, as fuelvapor is desorbed by the adsorbent in the canister, heat is consumed. Inthis way, the adsorption and desorption of fuel vapor by the canistermay be monitored and estimated based on temperature changes within thecanister.

Vent line 227 may also allow fresh air to be drawn into canister 222when purging stored fuel vapors from fuel system 218 to engine intake223 via purge line 228 and purge valve 261. For example, purge valve 261may be normally closed but may be opened during certain conditions sothat vacuum from engine intake manifold 244 is provided to the fuelvapor canister for purging. In some examples, vent line 227 may includean air filter 259 disposed therein upstream of a canister 222.

In some examples, the flow of air and vapors between canister 222 andthe atmosphere may be regulated by a canister vent valve 297 coupledwithin vent line 227. When included, the canister vent valve 297 may bea normally open valve, so that fuel tank isolation valve 252 (FTIV) maycontrol venting of fuel tank 220 with the atmosphere. FTIV 252 may bepositioned between the fuel tank and the fuel vapor canister 222 withinconduit 278. FTIV 252 may be a normally closed valve, that when opened,allows for the venting of fuel vapors from fuel tank 220 to fuel vaporcanister 222. Fuel vapors may then be vented to atmosphere, or purged toengine intake system 223 via canister purge valve 261.

Fuel system 218 may be operated by controller 212 in a plurality ofmodes by selective adjustment of the various valves and solenoids. Forexample, the fuel system may be operated in a fuel vapor storage mode(e.g., during a fuel tank refueling operation and with the engine notcombusting air and fuel), wherein the controller 212 may open isolationvalve 252 while closing canister purge valve (CPV) 261 to directrefueling vapors into canister 222 while preventing fuel vapors frombeing directed into the intake manifold.

As another example, the fuel system may be operated in a refueling mode(e.g., when fuel tank refueling is requested by a vehicle operator),wherein the controller 212 may open isolation valve 252, whilemaintaining canister purge valve 261 closed, to depressurize the fueltank before allowing enabling fuel to be added therein. As such,isolation valve 252 may be kept open during the refueling operation toallow refueling vapors to be stored in the canister. After refueling iscompleted, the isolation valve may be closed.

As yet another example, the fuel system may be operated in a canisterpurging mode (e.g., after an emission control device light-offtemperature has been attained and with the engine combusting air andfuel), wherein the controller 212 may open canister purge valve 261while closing isolation valve 252. Herein, the vacuum generated by theintake manifold of the operating engine may be used to draw fresh airthrough vent 227 and through fuel vapor canister 222 to purge the storedfuel vapors into intake manifold 244. In this mode, the purged fuelvapors from the canister are combusted in the engine. The purging may becontinued until the stored fuel vapor amount in the canister is below athreshold.

Controller 212 may comprise a portion of a control system 14, asdiscussed above with regard to FIG. 1A. Control system 214 is shownreceiving information from a plurality of sensors 16 (various examplesof which are described herein) and sending control signals to aplurality of actuators 81 (various examples of which are describedherein. As one example, sensors 16 may include exhaust gas sensor 237located upstream of the emission control device 70B, temperature sensor233, pressure sensor 291, and canister temperature sensor 232. Othersensors such as pressure, temperature, air/fuel ratio, and compositionsensors may be coupled to various locations in the vehicle system 206.As another example, the actuators may include throttle 62B, fuel tankisolation valve 252, canister purge valve 261, and canister vent valve297. The control system 214 may include a controller 212. The controllermay receive input data from the various sensors, process the input data,and trigger the actuators in response to the processed input data basedon instruction or code programmed therein corresponding to one or moreroutines.

FIG. 3 is a block diagram of vehicle 121 including a powertrain ordriveline 300. The powertrain of FIG. 3 includes engine 110 shown inFIG. 1A-1B. Other components of FIG. 3 that are common with FIG. 1A areindicated by like numerals, and will be discussed in detail below.Powertrain 300 is shown including vehicle system controller 12, enginecontroller 111B, electric machine controller 352, transmissioncontroller 354, energy storage device controller 353, and brakecontroller 141 (also referred to herein as brake system control module).The controllers may communicate over controller area network (CAN) 399.Each of the controllers may provide information to other controllerssuch as torque output limits (e.g. torque output of the device orcomponent being controlled not to be exceeded), toque input limits (e.g.torque input of the device or component being controlled not to beexceeded), torque output of the device being controlled, sensor anactuator data, diagnostic information (e.g. information regarding adegraded transmission, information regarding a degraded engine,information regarding a degraded electric machine, information regardingdegraded brakes). Further, the vehicle system controller 12 may providecommands to engine controller 111B, electric machine controller 352,transmission controller 354, and brake controller 141 to achieve driverinput requests and other requests that are based on vehicle operatingconditions.

For example, in response to a driver releasing an accelerator pedal andvehicle speed decreasing, vehicle system controller 12 may request adesired wheel torque or wheel power level to provide a desired rate ofvehicle deceleration. The desired wheel torque may be provided byvehicle system controller 12 requesting a first braking torque fromelectric machine controller 352 and a second braking torque from brakecontroller 141, the first and second torques providing the desiredbraking torque at vehicle wheels 131.

In other examples, the partitioning of controlling powertrain devicesmay be partitioned differently than is illustrated in FIG. 3. Forexample, a single controller may take the place of vehicle systemcontroller 12, engine controller 111B, electric machine controller 352,transmission controller 354, and brake controller 141. Alternatively,the vehicle system controller 12 and the engine controller 111B may be asingle unit while the electric machine controller 352, the transmissioncontroller 354, and the brake controller 141 may be standalonecontrollers.

In this example, powertrain 300 may be powered by engine 110 andelectric machine 120. In other examples, engine 110 may be omitted.Engine 110 may be started with an engine starter (e.g. 140), via beltintegrated starter/generator (BISG) 142, or via electric machine 120. Insome examples, BISG may be coupled directly to the engine crankshaft ateither end (e.g., front or back) of the crankshaft. Electric machine 120(e.g. high voltage electric machine, operated with greater than 30volts), is also referred to herein as electric machine, motor, and/orgenerator. Further, torque of engine 110 may be adjusted via a torqueactuator 304, such as a fuel injector, throttle, etc.

BISG 142 is mechanically coupled to engine 110 via belt 331. BISG 142may be coupled to a crankshaft (not shown) or a camshaft (not shown).BISG 142 may operate as a motor when supplied with electrical power viaelectric energy storage device 132, also referred to herein as onboardenergy storage device 132. BISG 142 may additionally operate as agenerator supplying electrical power to electric energy storage device132.

Driveline 300 includes engine 110 mechanically coupled to dual clutchtransmission (DCT) 125 via crank shaft 341. DCT 125 includes a firstclutch 126, a second clutch 127, and a gear box 128. DCT 125 outputstorque to shaft 129, to supply torque to vehicle wheels 131.Transmission controller 354 selectively opens and closes first clutch126 and second clutch 127 to shift DCT 125.

Gear box 128 may include a plurality of gears. One clutch, for examplefirst clutch 126 may control odd gears 361 (e.g. first, third, fifth,and reverse), while another clutch, for example second clutch 127, maycontrol even gears 362 (e.g. second, fourth, and sixth). By utilizingsuch an arrangement, gears can be changed without interrupting powerflow from the engine 110 to dual clutch transmission 125.

Electric machine 120 may be operated to provide torque to powertrain 300or to convert powertrain torque into electrical energy to be stored inelectrical energy storage device 132 in a regeneration mode.Additionally, electric machine 120 may convert the vehicle's kineticenergy into electrical energy for storage in electric energy storagedevice 132. Electric machine 120 is in electrical communication withenergy storage device 132. Electric machine 120 has a higher outputtorque capacity than starter (e.g. 140) depicted in FIG. 1A, or BISG142. Further, electric machine 120 directly drives powertrain 300, or isdirectly driven by powertrain 300.

Electrical energy storage device 132 (e.g. high voltage battery or powersource) may be a battery, capacitor, or inductor. Electric machine 120is mechanically coupled to wheels 131 and dual clutch transmission via agear set in rear drive unit 136 (shown in FIG. 1A). Electric machine 120may provide a positive torque or a negative torque to powertrain 300 viaoperating as a motor or generator as instructed by electric machinecontroller 352.

Further, a frictional force may be applied to wheels 131 by engagingfriction wheel brakes 318. In one example, friction wheel brakes 318 maybe engaged in response to the driver pressing his foot on a brake pedal(e.g. 192) and/or in response to instructions within brake controller141. Further, brake controller 141 may apply brakes 318 in response toinformation and/or requests made by vehicle system controller 12. In thesame way, a frictional force may be reduced to wheels 131 by disengagingwheel brakes 318 in response to the driver releasing his foot from abrake pedal, brake controller instructions, and/or vehicle systemcontroller instructions and/or information. For example, vehicle brakesmay apply a frictional force to wheels 131 via controller 141 as part ofan automated engine stopping procedure.

Vehicle system controller 12 may also communicate vehicle suspensionsettings to suspension controller 380. The suspension (e.g. 111) ofvehicle 121 may be adjusted to critically damp, over damp, or under dampthe vehicle suspension via variable dampeners 381.

Accordingly, torque control of the various powertrain components may besupervised by vehicle system controller 12 with local torque control forthe engine 110, transmission 125, electric machine 120, and brakes 318provided via engine controller 111B, electric machine controller 352,transmission controller 354, and brake controller 141.

As one example, an engine torque output may be controlled by adjusting acombination of spark timing, fuel pulse width, fuel pulse timing, and/orair charge, by controlling throttle (e.g. 62B) opening and/or valvetiming, valve lift and boost for turbo- or super-charged engines. In thecase of a diesel engine, controller 12 may control the engine torqueoutput by controlling a combination of fuel pulse width, fuel pulsetiming, and air charge. In all cases, engine control may be performed ona cylinder-by-cylinder basis to control the engine torque output.

Electric machine controller 352 may control torque output and electricalenergy production from electric machine 120 by adjusting current flowingto and from field and/or armature windings of electric machine 120 as isknown in the art.

Transmission controller 354 may receive transmission output shaft torquefrom torque sensor 372. Alternatively, sensor 372 may be a positionsensor or torque and position sensors. If sensor 372 is a positionsensor, transmission controller 354 may count shaft position pulses overa predetermined time interval to determine transmission output shaftvelocity. Transmission controller 354 may also differentiatetransmission output shaft velocity to determine transmission outputshaft acceleration. Transmission controller 354, engine controller 111B,and vehicle system controller 12, may also receive additionaltransmission information from sensors 377, which may include but are notlimited to pump output line pressure sensors, transmission hydraulicpressure sensors (e.g., gear clutch fluid pressure sensors), motortemperature sensors, BISG temperatures, shift selector position sensors,synchronizer position sensors, and ambient temperature sensors.Transmission controller may also receive a requested transmission state(e.g., requested gear or park mode) from shift selector 379, which maybe a lever, switches, or other device.

Brake controller 141 receives wheel speed information via wheel speedsensor 195 and braking requests from vehicle system controller 12. Brakecontroller 141 may also receive brake pedal position information frombrake pedal sensor (e.g. 157) shown in FIG. 1A directly or over CAN 399.Brake controller 250 may provide braking responsive to a wheel torquecommand from vehicle system controller 255. Brake controller 141 mayalso provide anti-lock and vehicle stability braking to improve vehiclebraking and stability. As such, brake controller 141 may provide a wheeltorque limit (e.g., a threshold negative wheel torque not to beexceeded) to the vehicle system controller 12 so that negative motortorque does not cause the wheel torque limit to be exceeded. Forexample, if controller 12 issues a negative wheel torque limit of 50N-m, motor torque may be adjusted to provide less than 50 N-m (e.g., 49N-m) of negative torque at the wheels, including accounting fortransmission gearing.

Positive torque may be transmitted to vehicle wheels 131 in a directionstarting at engine 110 and ending at wheels 131. Thus, according to thedirection of positive torque flow in driveline 300, engine 110 ispositioned in driveline 300 upstream if transmission 125. Transmission125 is positioned upstream of electric machine 120, and BISG 142 may bepositioned upstream of engine 110, or downstream of engine 110 andupstream of transmission 125. Electric machine 120 is positioneddownstream of engine 110 and transmission 125.

FIG. 4 shows a detailed illustration of a dual clutch transmission (DCT)125. Engine crankshaft 40B is illustrated as coupling to a clutchhousing 493. Alternatively, a shaft may couple crankshaft 40B to clutchhousing 493. Clutch housing 493 may spin in accordance with rotation ofcrankshaft 40B. Clutch housing 493 may include a first clutch 126 and asecond clutch 127. Furthermore, each of first clutch 126 and secondclutch 127 have an associated first clutch plate 490, and a secondclutch plate 491, respectively. In some examples, the clutches maycomprise wet clutches, bathed in oil (for cooling), or dry plateclutches. Engine torque may be transferred from clutch housing 493 toeither first clutch 126 or second clutch 127. First transmission clutch126 transfers torque between engine 110 (shown in FIG. 1A) and firsttransmission input shaft 402. As such, clutch housing 493 may bereferred to as an input side of first transmission clutch 126 and 126Amay be referred to as an output side of first transmission clutch 126.Second transmission clutch 127 transfers torque between engine 110(shown in FIG. 1A) and second transmission input shaft 404. As such,clutch housing 493 may be referred to as an input side of secondtransmission clutch 127 and 127A may be referred to as an output side ofsecond transmission clutch 127.

A gear box 128 may include a plurality of gears, as discussed above.There are two transmission input shafts, including first transmissioninput shaft 402, and second transmission input shaft 404. Secondtransmission input shaft 404 is hollow, while first transmission inputshaft 402 is solid, and sits coaxially within the second transmissioninput shaft 404. As an example, first transmission input shaft 402 mayhave a plurality of fixed gears. For example, first transmission inputshaft 402 may include first fixed gear 406 for receiving first gear 420,third fixed gear 410 for receiving third gear 424, fifth fixed gear 414for receiving fifth gear 428, and seventh fixed gear 418 for receivingseventh gear 432. In other words, first transmission input shaft 402 maybe selectively coupled to a plurality of odd gears. Second transmissioninput shaft 404 may include second fixed gear 408 for receiving secondgear 422, or a reverse gear 429, and may further include fourth fixedgear 416, for receiving either fourth gear 426 or sixth gear 430. It maybe understood that both first transmission input shaft 402 and secondtransmission input shaft 404 may be connected to each of first clutch126 and second clutch 127 via spines (not shown) on the outside of eachshaft, respectively. In a normal resting state, each of first clutch 402and second clutch 404 are held open, for example via springs (notshown), etc., such that no torque from engine (e.g. 110) may betransmitted to first transmission input shaft 402 or second transmissioninput shaft 404 when each of the respective clutches are in an openstate. Responsive to closing first clutch 126, engine torque may betransmitted to first transmission input shaft 402, and responsive toclosing second clutch 127, engine torque may be transmitted to secondtransmission input shaft 404. During normal operation, transmissionelectronics may ensure that only one clutch is closed at any given time.

Gear box 128 may further include a first layshaft shaft 440, and secondlayshaft shaft 442. Gears on first layshaft shaft 440 and secondlayshaft shaft 442 are not fixed, but may freely rotate. In example DCT125, first layshaft shaft 440 includes first gear 420, second gear 422,sixth gear 430, and seventh gear 432. Second layshaft shaft 442 includesthird gear 424, fourth gear 426, fifth gear 428, and reverse gear 429.Both first layshaft shaft 440 and second layshaft shaft 442 may transfertorque via a first output pinion 450, and a second output pinion 452,respectively, to gear 453. In this way, both layshafts may transfertorque via each of first output pinion 450 and second output pinion 452,to output shaft 462, where output shaft may transfer torque to a reardrive unit 136 (shown in FIG. 1A) which may enable each of the drivenwheels (e.g. 131 of FIG. 1A) to rotate at different speeds, for examplewhen performing turning maneuvers.

As discussed above, each of first gear 420, second gear 422, third gear424, fourth gear 426, fifth gear 428, sixth gear 430, seventh gear 432,and reverse gear 429 are not fixed to layshafts (e.g. 440 and 442), butinstead may freely rotate. As such, synchronizers may be utilized toenable each of the gears to match the speed of the layshafts, and mayfurther be utilized to lock the gears. In example DCT 125, foursynchronizers are illustrated, for example, first synchronizer 470,second synchronizer 474, third synchronizer 480, and fourth synchronizer482. First synchronizer 470 includes corresponding first selector fork472, second synchronizer 474 includes corresponding selector fork 476,third synchronizer 480 includes corresponding third selector fork 478,and fourth synchronizer 484 includes corresponding fourth selector fork482. Each of the selector forks may enable movement of eachcorresponding synchronizer to lock one or more gears, or to unlock oneor more gears. For example, first synchronizer 440 may be utilized tolock either first gear 420 or seventh gear 432. Second synchronizer 474may be utilized to lock either second gear 422 or sixth gear 430. Thirdsynchronizer 480 may be utilized to lock either third gear 424 or fifthgear 428. Fourth synchronizer 484 may be utilized to lock either fifthgear 426, or reverse gear 429. In each case, movement of thesynchronizers may be accomplished via the selector forks (e.g. 472, 476,478, and 482) moving each of the respective synchronizers to the desiredposition.

Movement of synchronizers via selector forks may be carried out viatransmission control module (TCM) 354 and shift fork actuators 488,where TCM 354 may comprise TCM 354 discussed above with regard to FIG.3. TCM 354 may collect input signals from various sensors, assess theinput, and control various actuators accordingly. Inputs utilized by TCM354 may include but are not limited to transmission range (P/R/N/D/S/L,etc.), vehicle speed, engine speed and torque, throttle position, enginetemperature, ambient temperature, steering angle, brake inputs, gear boxinput shaft speed (for both first transmission input shaft 402 andsecond transmission input shaft 404), vehicle attitude (tilt). The TCMmay control actuators via an open-loop control, to allow for adaptivecontrol. For example, adaptive control may enable TCM 354 to identifyand adapt to clutch engagement points, clutch friction coefficients, andposition of synchronizer assemblies. TCM 354 may also adjust firstclutch actuator 489 and second clutch actuator 487 to open and closefirst clutch 126 and second clutch 127.

As such TCM 354 is illustrated as receiving input from various sensors377. As discussed above with regard to FIG. 3, the various sensors mayinclude pump output line pressure sensors, transmission hydraulicpressure sensors (e.g. gear clutch fluid pressure sensors), motortemperature sensors, shifter position sensors, synchronizer positionsensors, and ambient temperature sensors. The various sensors 377 mayfurther include wheel speed sensors (e.g. 195), engine speed sensors,engine torque sensors, throttle position sensors, engine temperaturesensors, steering angle sensors, and inertial sensors (e.g. 199).Inertial sensors may comprise one or more of the following:longitudinal, latitudinal, vertical, yaw, roll, and pitch sensors, asdiscussed above with regard to FIG. 1A.

Sensors 377 may further include an input shaft speed (ISS) sensor, whichmay include a magneto-resistive sensor, and where one ISS sensor may beincluded for each gear box input shaft (e.g. one for first transmissioninput shaft 402 and one for second transmission input shaft 404).Sensors 377 may further include an output shaft speed sensor (OSS),which may include a magneto-resistive sensor, and may be attached tooutput shaft 462. Sensors 377 may further include a transmission range(TR) sensor, which may be utilized by the TCM to detect position ofselector forks (e.g. 472, 476, 478, 482).

DCT 125 may be understood to function as described herein. For example,when first clutch 126 is actuated closed, engine torque may be suppliedto first transmission input shaft 402. When first clutch 126 is closed,it may be understood that second clutch 127 is open, and vice versa.Depending on which gear is locked when first clutch 126 is closed, powermay be transmitted via the first transmission input shaft 402 to eitherfirst layshaft 440 or second layshaft 442, and may be furthertransmitted to output shaft 462 via either first pinion gear 450 orsecond pinion gear 452. Alternatively, when second clutch 127 is closed,power may be transmitted via the second transmission input shaft 404 toeither first layshaft 440 or second layshaft 442, depending on whichgear is locked, and may be further transmitted to output shaft 462 viaeither first pinion gear 450 or second pinion gear 452. It may beunderstood that when torque is being transferred to one layshaft (e.g.first layshaft 440), the other layshaft (e.g. second layshaft 442) maycontinue to rotate even though only the one shaft is driven directly bythe input. More specifically, the non-engaged shaft (e.g. secondlayshaft 442) may continue to rotate as it is driven indirectly by theoutput shaft 462 and respective pinion gear (e.g. 452).

DCT 125 may enable preselection of gears, which may thus enable rapidswitching between gears with minimal loss of torque during shifting. Asan example, when first gear 420 is locked via first synchronizer 440,and wherein first clutch 126 is closed (and second clutch 127 is open),power may be transmitted from the engine to first input shaft 402, andto first layshaft 440. While first gear 420 is engaged, second gear 422may simultaneously be locked via second synchronizer 474. Because secondgear 422 is locked, this may rotate second input shaft 404, where thesecond input shaft 404 is speed matched to the vehicle speed in secondgear. In an alternative case where a gear is pre-selected on the otherlayshaft (e.g. second layshaft 442), that layshaft will also rotate asit is driven by output shaft 462 and pinion 452.

When a gear shift is initiated by TCM 354, only the clutches need to beactuated to open first clutch 126 and close second clutch 127.Furthermore, outside the TCM, engine speed may be lowered to match theupshift. With the second clutch 127 closed, power may be transmittedfrom the engine, to second input shaft 404, and to first layshaft 440,and may be further transmitted to output shaft 462 via pinion 450.Subsequent to the shifting of gears being completed, TCM 354 maypre-select the next gear appropriately. For example, TCM 354 maypre-select either a higher or a lower gear, based on input it receivesfrom various sensors 377. In this way, gear changes may be achievedrapidly with minimal loss of engine torque provided to the output shaft462.

Dual clutch transmission 400 may in some examples include a parking gear460. A parking pawl 463 may face parking gear 460. When a shift lever isset to park, park pawl 463 may engage parking gear 460. Engagement ofparking pawl 463 with parking gear 460 may be accomplished via a parkingpawl spring 464, or may be achieved via a cable (not shown), a hydraulicpiston (not shown) or a motor (not shown), for example. When parkingpawl 463 is engaged with parking gear 460, driving wheels (e.g. 130,131) of a vehicle may be locked. On the other hand, responsive to theshift lever being moved from park, to another selection (e.g. drive),parking pawl 463 may move such that parking pawl 463 may be disengagedfrom parking gear 460.

In some examples, an electric transmission pump 412 may supply hydraulicfluid from transmission sump 411 to compress spring 464, in order torelease parking pawl 463 from parking gear 460. Electric transmissionpump 412 may be powered by an onboard energy storage device (e.g. 132),for example. In some examples, a mechanical pump 467 may additionally oralternatively supply hydraulic fluid from transmission sump 411 tocompress spring 464 to release parking pawl 463 from parking gear 460.While not explicitly illustrated, mechanical pump may be driven by theengine (e.g. 110), and may be mechanically coupled to clutch housing493. A park pawl valve 461 may regulate the flow of hydraulic fluid tospring 464, in some examples.

The system of FIGS. 1A-4 provides for a system, comprising: an engine; adual clutch transmission coupled to the engine, the dual clutchtransmission not including a parking pawl; an electric machine coupledto dual clutch transmission; and a controller including executableinstructions stored in non-transitory memory to request rotation of anelectric machine in response to an indication that a first gear or asecond gear is not engaged after the dual clutch transmission has beencommanded to a park state. In a first example of the system, the systemfurther includes where an output shaft of the transmission is held fromrotating when the dual clutch transmission is in the park state. Asecond example of the system optionally includes the first example, andfurther comprises synchronizers for the first and second gears. A thirdexample of the system optionally includes any one or more or each of thefirst and second examples, and further comprises sensors to determineoperating states of the synchronizers. A fourth example of the systemoptionally includes any one or more or each of the first through thirdexamples, and further comprises additional instructions to establishwhether or not the first gear and the second gear are engaged inresponse to output of the sensors.

The system of FIGS. 1A-4 also provides for a system, comprising: anengine; a dual clutch transmission coupled to the engine, the dualclutch transmission including a parking pawl and a hydraulic pump influidic communication with the parking pawl; an electric machine coupledto dual clutch transmission; and a controller including executableinstructions stored in non-transitory memory to disengage the parkingpawl via supplying hydraulic fluid to the parking pawl via the hydraulicpump in response to a request to propel a vehicle via power suppliedsolely from the electric machine. In a first example, the system furtherincludes where the hydraulic pump is electrically driven via an electricmotor, the electric motor not coupled to the engine. A second example ofthe system optionally includes the first example, and further comprisesadditional instructions to rotate the hydraulic pump via the electricmotor in response to the request to propel the vehicle via powersupplied solely from the electric machine, and where the electricmachine is not the electric motor. A third example of the systemoptionally includes any one or more or each of the first and secondexamples, and further comprises additional instructions to rotate thehydraulic pump via the engine without starting the engine. A fourthexample of the system optionally includes any one or more or each of thefirst through third examples and further includes where the parking pawlincludes a spring for engaging the parking pawl.

Turning to FIG. 5 a high level flowchart for an example method 500 forentering into an exiting a vehicle transmission park state, is shown.More specifically, method 500 may include engaging a first gear andengaging a second gear of a dual clutch transmission in response to arequest to enter a vehicle park state where an output of a transmissionis held from rotating, and where the first gear is coupled to a firstlayshaft, the second gear coupled to a second layshaft. In someexamples, method 500 may include selecting the first gear and the secondgear responsive to vehicle grade.

Method 500 will be described with reference to the systems describedherein and shown in FIGS. 1A-4, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 500 may be carried out by acontroller, such as controller 354 in FIG. 3, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 500 and the rest of the methodsincluded herein may be executed by the various controllers describedherein based on instructions stored on a memory of the respectivecontrollers and in conjunction with signals received from sensors of theengine system, such as the sensors described above with reference toFIGS. 1A-4. The controller 354 may communicate with other controllersdescribed herein to employ driveline actuators such as electric machine(e.g. 120), selector forks (e.g. 472, 476, 478, 482), etc., according tothe methods depicted below.

Method 500 begins at 505 and may include indicating whether a vehiclepark state is requested. For example, a vehicle park state may berequested by a vehicle operator attempting to engage a shift lever to apark selection. If, at 505, a vehicle park state is indicated to berequested, method 500 may proceed to 510, and may include indicatingwhether vehicle speed is less than (L.T.) a threshold speed. In someexamples, the threshold speed may comprise a vehicle speed of 2.5 mph.Vehicle speed may be indicated via wheel speed sensors (e.g. 195), forexample. If, at 510, vehicle speed is indicated to be above thethreshold speed, method 500 may proceed to 515. At 515, method 500 mayinclude informing the vehicle operator (also referred to herein as adriver), that the vehicle park state may not be entered until vehiclespeed is reduced. Such an indication may be communicated to the drivervia one or more of an audible indication, an indication on a displaysystem on a vehicle dash, etc. Method 500 returns to 510 after providingthe indication to the operator. Thus, method 500 may include notengaging the first and second gears unless vehicle speed is less than athreshold speed.

Responsive to an indication that vehicle speed is below the vehiclespeed threshold at 510, method 500 may proceed to 520. At 520, method500 may include commanding gear synchronizers (e.g., 470 of FIG. 4) toengage two gears (e.g. the first gear and the second gear), on the twolayshafts (e.g. 440 and 442). Simultaneously commanding synchronizers toengage two gears at 520 may include the controller selecting which ofthe synchros or synchronizers to utilize to engage the first gear andthe second gear). For example, the controller may receive informationabout vehicle grade via an accelerometer (e.g. 20), or inclinometer(e.g. 21), and an appropriate first gear and appropriate second gear maybe indicated, where the appropriate first gear and appropriate secondgear may be a function of road grade. With an appropriate first gear andsecond gear indicated, the controller may thus select whichsynchronizers to utilize to engage the selected first gear and secondgear. It may be understood that in the description herein, first gearmay refer to any gear positioned on the first layshaft, while secondgear may refer to any gear positioned on the second layshaft. It may befurther understood that any of one of the gears positioned on the firstlayshaft may be engaged, and any one of the gears positioned on thesecond layshaft may be engaged, where the determination of what gears toengage on the first layshaft and the second layshaft may be a functionof road grade. As one example, based on an indicated road grade, firstgear may comprise sixth gear (e.g. 430), and second gear may comprisefourth gear (e.g. 426) for a road with a first grade. During a conditionof a different road grade a different first gear, such as first gear,and a second gear, such as third gear, may be engaged responsive to thedifferent road grade (e.g., a second road grade). Further, duringconditions of no gear degradation, first and second gears may be a firstgroup of gears, and during conditions of gear degradation, first andsecond gears may be a second group of gears. Such examples are meant tobe illustrative, and are not meant to be limiting. By selecting whichgear to engage on the first layshaft and which gear to engage on thesecond layshaft as a function of road grade, wear on gears associatedwith the first and second layshafts may be reduced. It may be furtherunderstood that, responsive to selection of which gear on the firstlayshaft to engage, and which gear on the second layshaft to engage, thecontroller may command the appropriate selector fork to move theappropriate synchronizers to the selected first gear and second gear. Insuch a fashion, the controller may command appropriate synchronizers toengage two gears on the two layshafts at 520. Furthermore, at 525,method 500 may include opening a first clutch (e.g. 126) coupled to thefirst gear before the first gear is engaged, and opening a second clutch(e.g. 127) coupled to the second gear before the second gear is engaged.In this way, the layshafts may be decoupled from the engine crankshaftduring gear engagement to avoid engine motion if the synchronizers donot fully engage the gears to be engaged.

Proceeding to 525, method 500 may include indicating whether thesynchronizers are engaged. For example, position sensors (e.g.transmission range sensors 377) on each of the synchronizers may beutilized to indicate whether the synchronizers are engaged with thefirst gear and second gear. Responsive to an indication that one or bothof the synchronizers are not engaged, method 500 may proceed to 530, andmay include rotating a transmission output shaft (e.g. 462) via anelectric machine (e.g. 120). More specifically, in attempting to engagethe synchronizers, under some conditions synchro teeth may be alignedwhich may thus result in synchro blocking. Thus, at 530, the electricmachine may be utilized to resolve the issue of synchro blocking, viaapplying a rotation to the transmission output shaft, thus resolving theblocked condition. Responsive to rotating the transmission output shaftvia the electric machine, position sensors on the synchronizers may beutilized to indicate when the synchronizers are engage, as discussedabove. Furthermore, at 530, rotation of the electric machine maycomprise communicating a request to rotate the electric machine from atransmission controller (e.g. 354) to an electric machine controller(e.g. 352). The electric machine may be rotated in a forward or reversedirection.

Thus, it may be understood that method 500 may include commanding thefirst gear engaged and commanding the second gear engaged, in responseto a request to enter a vehicle park state where the output shaft of thetransmission is held from rotating, and may further include rotating theelectric machine coupled to the output shaft of the transmission inresponse to an indication that the first gear or second gear is notengaged.

Responsive to an indication that the synchronizers are engaged at 525,method 500 may proceed to 535. At 535, method 500 may include indicatingthat the vehicle is in park. For example, an indication that the vehicleis in park may be communicated to the vehicle controller, and may befurther communicated to the vehicle operator, for example via an audibleindication, or via an indication on the display system on the vehicledash.

Proceeding to 540, method 500 may include indicating whether a requestto exit the vehicle park state is requested. As an example, a request toexit the vehicle park state may include the vehicle operator adjusting ashift selector to a position other than park. Responsive to an exit fromthe vehicle park state being requested, method 500 may proceed to 545,and may include indicating whether the vehicle is parked on a hill, orslope, greater than (G.T.) a slope threshold. The slope threshold maycomprise a slope wherein a typical synchro and selector fork may nothave the force desired to disengage the synchro from either or both ofthe first and second gears. As described above road grade may beindicated via an accelerometer or an inclinometer. Thus, at 545, if itis indicated that the vehicle is not parked on a slope greater than theslope threshold, method 500 may proceed to 555.

At 555, method 500 may include commanding the first gear or the secondgear disengaged in response to the request to exit the vehicle parkstate. In other words, at 555, method 500 may include commanding thesynchronizers to disengage at least one gear on the two layshafts.Commanding the first gear or the second gear disengaged may include thecontroller commanding the synchronizers engaged with the first gear orthe second gear to be disengaged from the first gear or second gear. Forexample, the selector forks associated with the engaged synchronizersmay be controlled via the controller to move the synchronizers engagedwith the first gear or second gear to a disengaged position.

Alternatively, returning to 545, responsive to an indication that thevehicle is parked on a slope greater than the slope threshold, method500 may proceed to 550, and may include rotating the transmission outputshaft via the electric machine. The electric machine may rotate in aforward or reverse direction. Thus, method 500 may include rotating theelectric machine to unload the first gear or second gear in responsiveto the road grade, or slope, greater than the slope threshold. Byrotating the electric machine to rotate the transmission output shaft,the force for moving the appropriate synchronizers via the appropriateselector forks may be reduced, thus enabling the synchronizers engagedwith the first gear or second gear to a disengaged position.

As discussed, at 555, method 500 may include commanding thesynchronizers to disengage at least one gear on the two layshafts.Proceeding to 560, method 500 may include indicating whether the synchroor synchronizers are disengaged. As discussed above, position sensors oneach of the plurality of synchronizers may communicate with thecontroller to provide an indication as to whether the synchronizers aredisengaged. Responsive to an indication that the one or moresynchronizers are not disengaged, method 500 may proceed to 565. At 565,method 500 may include rotating the electric machine couple to thetransmission in response to the indication that the first gear or thesecond gear is not disengaged after commanding the first gear or secondgear disengaged. By rotating the electric machine, which may thus rotatethe output shaft coupled to the transmission, the engaged synchro orsynchronizers may be freed to disengage. Accordingly, responsive torotating the transmission output shaft via the electric machine at 565,method 500 may return to 555, and may include again commanding thesynchronizers to disengage at least one gear on the two layshafts, asdiscussed above.

Returning to 560, responsive to an indication that they synchronizersare disengaged, method 500 may proceed to 570, and may includeindicating the vehicle transmission state. For example, depending onwhich synchro was disengaged, the still engaged either first gear orsecond gear may control transmission output. Accordingly, thetransmission gearing state may be communicated to the vehiclecontroller, and may be further indicated via a display system on thevehicle dash, for example.

Method 500 may be enabled, for example, by a system comprising anengine, a dual clutch transmission not including a parking pawl, anelectric machine coupled to the dual clutch transmission, and acontroller including executable instructions in non-transitory memory torequest rotation of an electric machine in response to an indicationthat a first gear or a second gear is not engaged after the dual clutchtransmission has been commanded to a park state. In such a system, anoutput shaft of the transmission may be held from rotating when the dualclutch is in the park state. The system may further comprisesynchronizers for the first and second gears. The system may furthercomprise sensors (e.g. position sensors) to determine operating statesof the synchronizers. Still further, the system may comprise additionalinstructions to establish whether or not the first gear and the secondgear are engaged in response to output of the sensors.

Thus, the method of FIG. 5 provides for a driveline operating method,comprising: in response to a first condition, engaging a first gear andengaging a second gear of a dual clutch transmission in response to arequest to enter a vehicle park state where an output of a transmissionis held from rotating, the first gear coupled to a first layshaft, thesecond gear coupled to a second layshaft; and in response to a secondcondition, engaging a third gear and engaging a fourth gear of a dualclutch transmission in response to a request to enter a vehicle parkstate where an output of a transmission is held from rotating, the thirdgear coupled to a first layshaft, the fourth gear coupled to a secondlayshaft. In one example, the first and second conditions are first andsecond road grades. In another example, the first and second conditionsare first and second vehicle conditions (e.g., an indication of degradedgears and no indication of degraded gears).

In a first example of the method, the method further comprises opening afirst clutch coupled to the first gear before the first gear is engagedand opening a second clutch coupled to the second gear before the secondgear is engaged and holding the first and second clutches open whileengaging the first and second gears. A second example of the methodoptionally includes the first example, and further comprises notengaging the first and second gears unless vehicle speed is less than athreshold speed. A third example of the method optionally includes anyone or more or each of the first and second examples, and furthercomprises commanding the first gear or second gear disengaged inresponse to a request to exit the vehicle park state. A fourth exampleof the method optionally includes any one or more or each of the firstthrough third examples and further comprises rotating an electricmachine coupled to the transmission in response to an indication thatthe first gear or second gear is not disengaged after commanding thefirst gear or second gear disengaged. A fifth example of the methodoptionally includes any one or more or each of the first through fourthexamples and further comprises rotating an electric machine to unloadthe first gear or second gear in response to a road grade greater than athreshold. A sixth example of the method optionally includes any one ormore or each of the first through fifth examples and further includeswhere road grade is estimated via an accelerometer or an inclinometer.

The method of FIG. 5 also provides for a driveline operating method,comprising: simultaneously commanding a first gear engaged andcommanding a second gear engaged, the first gear coupled to a firstlayshaft, the second gear coupled to a second layshaft, in response to arequest to enter a vehicle park state where an output shaft of atransmission is held from rotating; and rotating an electric machinecoupled to the output shaft of the transmission in response to anindication that the first gear or second gear is not engaged. In a firstexample of the method, the method further comprises opening a firstclutch coupled to the first gear before the first gear is engaged andopening a second clutch coupled to the second gear before the secondgear is engaged and holding the first and second clutches open whileengaging the first and second gears. A second example of the methodoptionally includes the first example, and further comprises notengaging the first and second gears unless vehicle speed is less than athreshold speed. A third example of the method optionally includes anyone or more or each of the first and second examples, and furthercomprises commanding the first gear or second gear disengaged inresponse to a request to exit the vehicle park state.

In some examples, a fourth example of the method optionally includes anyone or more or each of the first through third examples, and furthercomprises rotating an electric machine coupled to the transmission inresponse to an indication that the first gear or second gear is notdisengaged after commanding the first gear or second gear disengaged. Afifth example of the method optionally includes any one or more or eachof the first through fourth examples, and further comprises rotating anelectric machine to unload the first gear or second gear in response toa road grade greater than a threshold. A sixth example of the methodoptionally includes any one or more or each of the first through fifthexamples, and further comprises communicating a request to rotate theelectric machine from a transmission controller to an electric machinecontroller. A seventh example of the method optionally includes any oneor more or each of the first through sixth examples, and furthercomprises providing the indication that the first gear or second gear isnot engaged in response to a position of a gear synchronizer.

The method of FIG. 5 also provides for a driveline operating method,comprising simultaneously commanding a first gear engaged and commandinga second gear engaged, the first gear coupled to a first layshaft, thesecond gear coupled to a second layshaft, in response to a request toenter a vehicle park state where an output shaft of a transmission isheld from rotating; rotating an electric machine coupled to the outputshaft of the transmission in response to an indication that the firstgear or second gear is not engaged; commanding the first gear or secondgear disengaged in response to a request to exit the vehicle park state;and rotating the electric machine coupled to the output shaft of thetransmission in response to an indication that the first gear or secondgear is not disengaged after commanding the first gear or second geardisengaged.

Turning to FIG. 6, an example timeline 600 is shown for conducting entryinto, and exit from, a vehicle transmission park state, according tomethod 500 described herein, and as applied to the systems describedherein and with reference to FIGS. 1A-4. Timeline 600 includes plot 605,indicating whether a vehicle park state is requested (active), or not(e.g., a bar over the word active, active bar), where the park state maybe requested via a vehicle operator (also referred to herein as adriver). Timeline 600 further includes plot 610, indicating whether anelectric machine (e.g. 120) is rotating, or not (rotating bar), overtime. Timeline 600 further includes plot 615, indicating a road gradethat the vehicle is traveling on, or is parked on, over time. Such anindication of road grade may be communicated to a vehicle controllervia, for example, an accelerometer, or inclinometer. Timeline 600further includes plot 620, indicating whether a first synchro is engagedwith a first gear, or not (engaged bar), and plot 625, indicatingwhether a second synchro is engaged with a second gear, or not (engagedbar), over time. Furthermore, timeline 600 further includes plot 630,indicating whether a transmission state is in park, or not (park bar),over time.

At time T0, a park request by the vehicle operator is not indicated,illustrated by plot 605. The electric machine is not rotating,illustrated by plot 610. Road grade not substantially inclined, ordeclined, indicated by plot 615. Furthermore, a first synchro is notengaged with a first gear, indicated by plot 620, and a second synchrois not engaged with a second gear, indicated by plot 625. As discussedabove with regard to method 500 depicted at FIG. 5, a first gear may beengage to a first layshaft (e.g., locked to the layshaft so that thegear rotates at a same speed as the layshaft), while a second gear maybe engaged to a second layshaft. As the first synchro and the secondsynchro are not engaged, the transmission state is in a state other thanpark, illustrated by plot 630.

At time T1, a park state is requested. Accordingly, the first synchro iscommanded by the controller to engage the first gear, and the secondsynchro is commanded by the controller to engage the second gear. Asdiscussed above, the choice of what gear constitutes the first gear, andwhat gear constitutes the second gear, may be determined by the vehiclecontroller as a function of road grade or other vehicle operatingcondition, such as a condition of gear degradation. The first gear maybe selected from any of the gears on the first layshaft, and the secondgear may be selected from any of the gears on the second layshaft. Byengaging both the first gear, and the second gear via the first andsecond synchronizers, the vehicle transmission is entered into a parkstate, indicated by plot 630. More specifically, by engaging both thefirst synchro with the first gear, and the second synchro with thesecond gear, an output shaft (e.g. 462) of the transmission may belocked, thus placing the vehicle in the park state. Furthermore, it maybe understood that engaging the synchronizers may include the controllercommanding the synchronizers to move to the desired gears, via selectorforks associated with the synchronizers, as discussed above.

Between time T1 and T2, the vehicle is maintained in the park state. Attime T2, a request to exit the park state is initiated. Such a requestmay include a shift lever being moved from the park position, to anotherposition, for example. Responsive to the request to exit the park state,the first synchro and the second synchro may be commanded to disengagefrom the first gear and second gear, respectively. As discussed, such anaction may be initiated via communication between the controller andselector forks associated with the synchronizers.

However, at time T2, only the second synchro is indicated to bedisengaged responsive to the command to disengage both the first andsecond synchro. Accordingly, at time T3, the electric machine iscommanded on, whereby rotation of the electric machine may rotate thetransmission output shaft. By rotating the transmission output shaft,the first synchro may be freed to disengage from the first gear.Accordingly, with the electric machine activated between time T3 and T4,the first synchro is indicated to disengage from the first gear, and assuch, the transmission state is indicated to exit the park state.

The vehicle may be driven for a duration between time T4 and T5. At timeT5, another request for entry into a parked state is initiated,indicated by plot 605. Furthermore, the vehicle is indicated to be on aroad grade substantially steeper than between time T0 and T4. It may beunderstood that the road grade indicated at time T5 is greater than athreshold slope.

Responsive to the request for entry into the parked state at time T5, afirst gear and a second gear may be selected to engage, where, asdiscussed above, the first and second gear combination may be selectedas a function of road grade. For example, the vehicle controller mayreceive information pertaining to the current road grade, and responsiveto the request for entry to the parked state, the first gear and secondgear may be selected in order to minimize wear on the gears. Thus, itmay be understood that any of the gears on the first layshaft may beselected as the first gear, and any of the gears on the second layshaftmay be selected as the second gear. Furthermore, it may be understoodthat the gear selection at time T5 may be different than the gearselection at time T1, for example, as the road grade is differentbetween the two time points.

Responsive to the first and second gear being selected, appropriatefirst and second synchronizers may be selected for which to engage thefirst and second gears. The synchronizers may be commanded via thecontroller to engage the first and second gears, which may includecommanding the selector forks associated with the selected synchronizersto move the selected synchronizers for engagement with the first andsecond gears. Accordingly, at time T5, both the first and second syncrosare indicated to be engaged, where an indication of the engagement ofeach of the first and second synchronizers may communicated to thevehicle controller by position sensors associated with the first andsecond synchronizers. As both the first and second synchronizers areindicated to be engaged, it is further indicated that the vehicletransmission has entered into a park state, illustrated by plot 630.

The vehicle transmission remains in park between time T5 and T6. At timeT6, a request for exit from the park state is again indicated. Becausethe request for exit from the park state occurs while the vehicle isparked on a road grade above the slope threshold, the electric machinemay be activated in order to free the first synchro and second synchro,such that the first and second synchronizers may be readily disengaged.In other words, a force to disengage the first and second synchronizersmay be reduced by activating the electric machine, where activating theelectric machine includes rotating the electric machine, therebyrotating the transmission output shaft (e.g. 462). By activating theelectric machine, both the first synchro and second synchro are readilydisengaged.

Method 500 as depicted above pertains to entry into, and exit from, apark state, wherein the park state may be achieved via two gears onseparate layshafts being simultaneously engaged, such that atransmission output shaft is prevented from rotating. Such a method maybe utilized to achieve a park state without the use of a park pawl, suchas park pawl (e.g. 463) and associated park gear (e.g. 460), depicted atFIG. 4.

Turning now to FIG. 7, a method for entry into and exit from a parkstate, via the use of a park pawl, is shown. More specifically, method700 may comprise a driveline operating method, including engaging aparking pawl to an output shaft of a dual clutch transmission inresponse to a request to enter a vehicle into a parked state, anddisengaging the parking pawl via rotating an engine via an integratedstarter/generator in response to a request to propel the vehicle solelyvia power of an electric machine positioned downstream of the dualclutch transmission. In another example, method 700 may includedisengaging the parking pawl via activating an electric pump in responseto a request to propel the vehicle solely via power of an electricmachine positioned downstream of the dual clutch transmission. Bypropelling the vehicle solely via power of the electric machine, fuelsupplied to the engine may be conserved.

Method 700 will be described with reference to the systems describedherein, and shown in FIGS. 1A-4, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 700 may be carried out by acontroller, such as transmission controller 354 in FIG. 3, and may bestored at the controller as executable instructions in non-transitorymemory. Instructions for carrying out method 700 and the rest of themethods included herein may be executed by the various controllersdescribed herein based on instructions stored on a memory of therespective controllers and in conjunction with signals received fromsensors of the engine system, such as the sensors described above withreference to FIGS. 1A-4. The controller may communicate with othercontrollers described herein to employ driveline actuators such aselectric pump (e.g. 412), park pawl valve (e.g. 461), electric machine(e.g. 120), ISG (e.g. 142), fuel injectors (e.g. 266), etc., accordingto the methods depicted below.

Method 700 begins at 705 and may include indicating whether a vehiclepark mode is requested. For example, a vehicle park mode being requestedmay include a vehicle operator selecting a park mode from a shift leverin the vehicle. Proceeding to 710, method 700 may include indicatingwhether vehicle speed is lower than a threshold speed. In some examples,the threshold speed may be the same threshold speed as indicated abovewith regard to method 500 (e.g. 2.5 miles per hour). However, in otherexamples, the threshold speed may be different than that indicated aboveat FIG. 5. If, at 710, vehicle speed is not lower than the thresholdspeed, method 700 may proceed to 715, and may include indicating thatthe park function may not engage at vehicle speeds above the thresholdspeed. Such an indication may be communicated to a vehicle operator viaan audible indication, and/or visually via a display system on thevehicle dash, for example. Furthermore, such an indication may becommunicated to the vehicle controller. Method 700 returns to 710 afterproviding the indication.

Responsive to the vehicle park mode being requested at 705, and furtherresponsive to vehicle speed below the threshold speed at 710, method 700may proceed to 720. At 720, method 700 may include engaging the parkingpawl (e.g. 463) with the parking gear (e.g. 460), via a spring (e.g.464), for example. In some examples, at 720, method 700 may furtherinclude stopping the vehicle engine responsive to the engine beingactivated and further responsive to a request from the vehicle operator,or vehicle controller, to stop the engine.

Thus, while in the park mode, the park pawl may be engaged with the parkgear, thus preventing the transmission output shaft (e.g. 462) fromrotating. Proceeding to 725, method 700 may include indicating whetherexit from the vehicle park mode is requested. As an example, a requestto exit the park mode may include the vehicle operator selecting atransmission state other than park on a shift selector. Responsive to anexit from the park mode being requested, method 700 may proceed to 730,and may include indicating whether an electric transmission pump (e.g.412) is present in the vehicle system. If an electric transmission pumpis indicated to be present, method 700 may proceed to 735, and mayinclude indicating whether an electric only drive mode is active. Forexample, electric only mode may include a mode wherein the vehicle ispropelled solely via an electric machine (e.g. 120 of FIG. 1A)positioned downstream of the dual clutch transmission. If, at 735, it isindicate that electric only drive mode is active, method 700 may proceedto 740.

At 740, method 700 may include rotating the electric transmission pumpwhile the engine is maintained stopped, or deactivated. For example,power to the electric pump may be provided via an onboard energy source(e.g. 132). As indicated at FIG. 4, the electric pump may receivehydraulic fluid from a sump (e.g. 411). Thus, subsequent to activatingthe electric transmission pump at 740, method 700 may proceed to 745,and may include commanding the parking pawl to be hydraulicallyreleased. Such an action may include commanding open park pawl valve461, for example. Responsive to compression of the spring, the park pawlmay become disengaged from the parking gear. Thus, subsequent toactivation of the electric pump, and further subsequent to coupling theelectric pump to the spring (e.g. 464), method 700 may proceed to 750,and may include indicating whether the parking pawl is released. Forexample, a pawl position sensor (e.g. 468) may be configured tocommunicate a position of the parking pawl to the controller.Alternatively, a small torque may be applied to transmission outputshaft (e.g., 462 via the electric machine (e.g., 120) while first andsecond clutches (e.g. 126 and 127) are open, if the transmission outputshaft rotates, it may be determined that the parking pawl is released.

If, at 750, it is indicated that the parking pawl is not released,method 700 may proceed to 760. At 760, method 700 may include startingthe engine to release the parking pawl via hydraulic pressure providedby the engine. More specifically, a mechanical pump (e.g. 467) may becoupled to the engine, and may be configured to deliver hydraulicpressure to the parking pawl. Thus, at 760, method 700 may includerotating the mechanical pump via the engine, and may further includereleasing the parking pawl after the indication that the parking pawlwas not released via the use of the electric pump. At 760, it may beunderstood that starting the engine may include providing fuel and sparkto the engine cylinders. While not specifically illustrated, it may befurther understood that, responsive to the indication that the parkingpawl was not released via the electric pump, method 700 may includedeactivating the electric pump at 760. Furthermore, while notspecifically illustrated, operating the mechanical pump to release thepark pawl may further include commanding open a park pawl valve todeliver hydraulic fluid to the spring associated the park pawl, asdiscussed above.

At 755, method 700 may include indicating that the parking pawl isreleased. Such an indication may be communicated to the controller, andmay be further communicated to the vehicle operator via a display systemon the vehicle dash, for example. While not specifically indicated,responsive to the parking pawl being released, method 700 may furtherinclude deactivating the engine (e.g. ceasing engine rotation), andoperating the vehicle under electric only mode, in examples where theparking pawl was not released via the electric pump. In other words,method 700 may include providing torque to the vehicle wheels via theelectric machine, in response to the parking pawl being released.

Returning to step 730, responsive to exit from the vehicle park modebeing requested, and further responsive to an electric pump not beingpresent in the vehicle system, method 700 may proceed to 765. At 765,method 700 may include indicating whether electric only drive mode isactive, as described above at step 735 of method 700. If, at 765,electric only mode is not indicated to be active, method 700 may proceedto 770, and may include starting the engine to release the parking pawlutilizing hydraulic pressure provided by the engine. Such an action isdescribed above with regard to step 760, and thus for brevity, will notbe reiterated.

Returning to step 765, if electric only drive mode is indicated to beactive, method 700 may proceed to 775, and may include rotating theengine unfueled and not combusting air and fuel via the integratedstarter/generator (ISG) (e.g. 142). In one example, intake or exhaustvalves of the engine are held in an open state while the engine isrotated via the ISG to reduce engine pumping work. It may be understoodthat the integrated starter/generator may be coupled to the engine, andmay receive power supplied via the onboard energy source (e.g. 132) torotate the engine unfueled. By rotating the engine unfueled via the ISG,the mechanical pump coupled to the engine that is configured to deliverhydraulic pressure to the parking pawl may be activated. Proceeding to780 method 700 may include commanding the parking pawl to behydraulically released, which may include commanding open the park pawlvalve, as discussed above, to direct hydraulic fluid to compress thespring associated with the park pawl, whereby compression of the springmay release the park pawl from the park gear, as discussed above.

Continuing to 785, method 700 may include indicating whether the parkpawl is released. As discussed above, such an indication may becommunicated to the controller via a pawl position sensor (e.g. 468)configured to indicate the position of the pawl with respect to the parkgear. Alternatively, indication of parking pawl release may be based onrotating the transmission output shaft 462 via electric machine (e.g.,120) as previously described.

If, at 785, it is indicated that the pawl is not yet released, method700 may include returning to 775, wherein the engine may be continued tobe rotated without fueling via the ISG. Alternatively, responsive to anindication at 785 that the park pawl is released, method 700 may proceedto 790, and may include stopping engine rotation, via terminating powersupplied via the ISG to rotate the engine. Continuing to 755, method 700may include indicating that the pawl is released, as discussed above.While not explicitly illustrated, where the electric only drive mode isindicated to be active, method 700 may further include providing torqueto the vehicle wheels via the electric machine responsive to theindication that the parking pawl is released.

Thus, the method of FIG. 7 provides for releasing a parking pawl viapressure of hydraulic fluid supplied to a spring actuated parking pawl.The hydraulic pressure may be provided via an electric pump or viarotating an engine that is coupled to the transmission via an integratedstarter/generator that is coupled to the engine. The method may beparticularly useful when the hybrid vehicle is operated in an electriconly drive or propulsion mode.

The method of FIG. 7 provides for a driveline operating method,comprising: engaging a parking pawl to an output shaft of a dual clutchtransmission in response to a request to enter a vehicle into a parkedstate; and disengaging the parking pawl via rotating an engine via anintegrated starter/generator in response to a request to propel thevehicle solely via power of an electric machine positioned downstream ofthe dual clutch transmission. In a first example of the method, themethod further comprises reducing pumping work of the engine in responseto the request to propel the vehicle solely via power of the electricmachine. A second example of the method optionally includes the firstexample, and further includes where the integrated starter/generator iscoupled to the engine. A third example of the method optionally includesany one or more or each of the first and second examples and furtherincludes where the engine is not combusting air and fuel while theparking pawl is engaged. A fourth example of the method optionallyincludes any one or more or each of the first through third examples,and further comprises rotating a pump via rotating the engine. A fifthexample of the method optionally includes any one or more or each of thefirst through fourth examples and further comprises supplying fluid viathe pump to release the parking pawl. A sixth example of the methodoptionally includes any one or more or each of the first through fifthexamples and further includes ceasing engine rotation in response to anindication that the parking pawl is released.

The method of FIG. 7 also provides for a driveline operating method,comprising: engaging a parking pawl to an output shaft of a dual clutchtransmission in response to a request to enter a vehicle into a parkedstate; and disengaging the parking pawl via activating an electric pumpin response to a request to propel the vehicle solely via power of anelectric machine positioned downstream of the dual clutch transmission.In a first example of the method, the method further comprisesdeactivating the electric pump in response to an indication that theparking pawl is released. A second example of the method optionallyincludes the first example, and further comprises providing torque tovehicle wheels via the electric machine in response to the parking pawlbeing released. A third example of the method optionally includes anyone or more or each of the first and second examples, and furthercomprises starting an engine in response to an indication that theparking pawl is not released after commanding the parking pawl released.A fourth example of the method optionally includes any one or more oreach of the first through third examples, and further comprises rotatinga mechanical pump via the engine and releasing the parking pawl afterthe indication that the parking pawl is not released. A fifth example ofthe method optionally includes any one or more or each of the firstthrough fourth examples, and further comprises deactivating the electricpump in response to the indication that the parking pawl is notreleased. A sixth example of the method optionally includes any one ormore or each of the first through fifth examples, and further includeswhere the parking pawl is engaged via a spring. A seventh example of themethod optionally includes any one or more or each of the first throughsixth examples, and further includes where the dual clutch transmissionis positioned in a vehicle driveline between an engine and the electricmachine.

Turning to FIG. 8, an example timeline 800 is shown for entry into andexit from a park state vehicle transmission park state, according tomethod 700 described herein, and as applied to the systems describedherein and with reference to FIGS. 1A-4. Timeline 800 includes plot 805,indicating whether a vehicle park request is indicated (active), or not(active bar), over time. Timeline 800 further includes plot 810,indicating whether an electric transmission pump is rotating, or notrotating (rotating bar), over time. Timeline 800 further includes plot815, indicating whether an electric transmission pump is present in thevehicle, or not (present bar). Timeline 800 further includes plot 820,indicating whether an engine is rotating, or not (rotating bar), overtime. Timeline 800 further includes plot 825, indicating whether avehicle transmission is in a park mode (park), or not (park bar), overtime.

At time T10, a request for park mode is not indicated, illustrated byplot 805. Furthermore, an electric transmission pump (e.g. 412) is notindicated to be present in the vehicle, indicated by plot 815. As such,no plot line is indicated for whether the electric pump is rotating ornot. The engine is not indicated to be rotating at time T10, illustratedby plot 820. However, the vehicle is in operation, as the transmissionis in a gear state other than park, illustrated by plot 825.

At time T11, a request for park mode is indicated. Such a request may beindicated via a vehicle operator selecting a park gear state on a shiftselector (e.g., 379), for example. Responsive to the request, thetransmission is locked in park mode, via engagement of a park pawl witha park gear, thus locking the transmission output shaft. Thus, at timeT11, the transmission is indicated to be in park mode, illustrated byplot 825.

Between time T11 and T12, the vehicle is maintained in a park state. Attime T12, exit from the park mode is requested, indicated by plot 805.Such a request may include the vehicle operator selecting a transmissiongear other than park, for example. Because an electric pump is notindicated in the vehicle, an electric pump may not be used to generatehydraulic pressure to compress a spring associated with the park pawl.Thus, to release the park pawl, the engine is rotated at time T12. Whilenot explicitly illustrated, it may be understood that the engine isrotated via an ISG (e.g. 142), where the ISG receives power from anonboard energy storage device (e.g. 132). As such, the engine is rotatedunfueled, and the rotation of the engine may result in rotation of amechanical transmission pump coupled to the engine. By activating themechanical pump via engine rotation, where the engine rotation comprisesunfueled operation without combustion, hydraulic pressure may bedirected to the spring associated with the park pawl. The hydraulicpressure may compress the spring, thus releasing the park pawl from thepark gear. Accordingly, between time T12 and T13, the engine is rotatedunfueled, and at time T13, the transmission state is indicated totransition to a state other than park, illustrated by plot 825. In someexamples, the release of the park pawl from the park gear may beindicated via a pawl position sensor.

Furthermore, at time T13, engine rotation is stopped. More specifically,power provided via the ISG to the engine in order to rotate the enginemay be terminated. Thus, after the transmission park state is indicatedto exit from park mode, the vehicle may be propelled via an electricmachine (e.g. 120). In other words, as discussed above with regard tomethod 700, it may be understood that electric only mode is activated.Thus, subsequent to rotating the engine to release the park pawl, theengine rotation may be abruptly stopped, whereby the vehicle may bepropelled solely via the electric machine.

The right side of timeline 800 illustrates an example wherein anelectric transmission pump is indicated to be present in the vehicle,illustrated by plot 815. Prior to time T14, the vehicle is indicated tobe in operation, as transmission gear state is in a state other thanpark, illustrated by plot 825. At time T14, a request for entry into thepark mode is indicated, where such an indication may be communicated tothe controller via a vehicle operator selecting a park gear on a shiftlever, for example. Responsive to the request, the park pawl may engagewith the park gear, as discussed above, thus locking the transmissionoutput shaft.

Between time T14 and T15, the vehicle is maintained in park mode. Attime T15, a request for exit from the park mode is indicated. Asdiscussed, such a request may include the vehicle operator selecting agear other than park on a shift lever. Because the vehicle includes anelectric pump configured to couple to the vehicle hydraulic pump system,at time T15 the electric pump is activated, via power supplied to theelectric pump via the onboard storage device, for example. With theelectric pump activated, hydraulic pressure is provided to the springassociated with the park pawl. As discussed, the hydraulic pressure maycompress the spring, such that the park pawl may be released from thepark gear. Thus, between time T15 and T16, the electric pump ismaintained activated. At time T16, the transmission state is indicatedto transition from park, to a gear selection other than park,illustrated by plot 825. Furthermore, while not explicitly illustrated,it may be understood that electric only mode is activated. Thus, enginethe engine is maintained off, and it may be understood that after timeT16, the vehicle may be propelled solely via power from the electricmachine.

Referring now to FIG. 9, a flowchart of a method for operating adriveline of a hybrid vehicle powertrain 100 is shown. The method ofFIG. 9 may be incorporated into the system of FIGS. 1A-4 as executableinstructions stored in non-transitory memory of one or more controllers.Additionally, portions of the method of FIG. 9 may be actions performedvia the controllers shown in FIGS. 1A-4 to transform a state of a deviceor actuator in the real world. The method shown in FIG. 9 may operate inconjunction and cooperation with other methods described herein.

At 905, method 900 judges if a transmission upshift of a dual clutchtransmission (DCT) is expected within a threshold amount of time. In oneexample, method 900 judges if speed of a vehicle in which the DCToperates will reach a transmission upshift speed stored in controllermemory as a transmission shift schedule within the threshold amount oftime (e.g., 0.5 seconds). Method 900 may make the judgement based onpresent vehicle speed, transmission upshift speed for the present gearto the next highest gear, and rate of vehicle acceleration. For example,if a shift is expected at 45 KPH, vehicle speed is 40 KPH, and thevehicle is accelerating at 10 KPH/s, then method 400 may judge anupshift is expected within the threshold amount of time. If method 900judges that an upshift is expected within the threshold amount of time,the answer is yes and method 900 proceeds to 910. Otherwise, the answeris no and method 900 proceeds to exit.

At 910, method 900 judges if wear of an on-coming clutch is greater than(G.T.) a threshold amount. The wear of a clutch may be estimated basedon an amount of pressure applied to the clutch and a torque transfercapacity of the clutch (e.g., an amount of torque the clutch maytransfer from an input side of the clutch to the output side of theclutch) at the pressure or via other means. For example, if a clutchtransfer function indicates that clutch torque capacity is 100 N-m at apressure of 20 KPA, but the clutch has a capacity of only 50 N-m at apressure of 20 KPA, method 900 may judge that the clutch wear exceeds athreshold. If method 900 judges that wear of the clutch is greater thana threshold amount, the answer is yes and method 900 proceeds to 915.Otherwise, the answer is no and method 900 proceeds to 920.

At 915, method 900 may select a different gear than the gear in theshift schedule described at 905. The different gear or new gear is agear that may be selectively engaged to a different clutch than the gearoutput from the shift schedule. For example, if the shift scheduleindicates a transmission gear shift from third gear (e.g., 424 in FIG.4) to fourth gear (e.g., 426 in FIG. 4) at a speed of 30 KPH, and fourthgear is selectively engaged to a second clutch (e.g., 127 in FIG. 4) viasynchronizers, then method 900 may instead schedule the shift to fifthgear (e.g., 428 in FIG. 4) from third gear in response to wear of secondclutch. Thus, the newly scheduled upshift changes from shifting with thesecond clutch to fourth gear to shifting with the first clutch to fifthgear. Method 900 proceeds to 920.

At 920, method 900 adjusts a position of shift forks for the upshift. Inparticular, method 900 positions forks to engage the synchronizer forthe on-coming gear (e.g., gear requested to be engaged) so that theon-coming gear may be engaged. Method 900 proceeds to 925.

At 925, method 900 determines a value of a vehicle stability metric orparameter for present vehicle operating conditions. The vehiclestability metric may be an amount of lateral vehicle acceleration, wheelslip, yaw, roll, or pitch. The vehicle stability metric may bedetermined from output of accelerometers, wheel speed sensors, and/orbody motion sensors. For example, a lateral acceleration sensor mayindicate vehicle lateral acceleration is 0.4 Gs to provide a value of0.4 for a vehicle stability metric or parameter. Method 900 proceeds to930.

At 930, method 900 judges if the vehicle stability metric determined at925 is less than a threshold. The threshold value may be empiricallydetermined and stored in controller memory. For example, the vehiclestability metric threshold value may be 0.9 Gs and the vehicle stabilitymetric may be 0.4 Gs. If method 900 judges that the value of the vehiclestability metric is greater than (G.T.) the threshold value, the answeris yes and method 900 proceeds to 940. Otherwise, the answer is no andmethod 900 proceeds to 935.

At 935, method 900 outputs a requested torque to the driveline andwheels via the engine and/or the electric machine (e.g., 120 of FIG.1A). In one example, the requested or desired torque is a wheel torque(e.g., an amount of torque to deliver to vehicle wheels). The requestedtorque may be determined based on accelerator pedal position and vehiclespeed. A first portion of the requested torque may be allocated to theengine while a second portion of the requested torque may be allocatedto the electric machine so that the sum of engine torque and electricmachine torque provides the requested torque at the vehicle wheels.Method 900 proceeds to exit after the requested torque is output.

At 940, method 900 judges if battery (e.g., electric energy storagedevice 132 in FIG. 1A) state of charge (SOC) is less than (L.T.) athreshold. The threshold SOC may be empirically determined and stored tocontroller memory. If SOC is less than a threshold, the battery maystore and accept additional charge. If method 900 judges that thepresent battery SOC is less than the threshold amount, the answer is yesand method 900 proceeds to 965. Otherwise, the answer is no and method900 proceeds to 945.

At 965, method 900 begins the requested upshift based on thetransmission shift schedule and absorbs transmission output shaft torquevia the electric machine (e.g., 120 of FIG. 1A) during an inertia phaseof the upshift. In one example, method 900 absorbs driveline torque viathe electric machine that could cause the vehicle stability metric toexceed the vehicle stability threshold. Alternatively, method 900absorbs driveline torque via the electric machine to reduce the vehiclestability metric to a value less than the vehicle stability threshold.

In one example, method 900 subtracts the value of the vehicle stabilitymetric from the vehicle stability threshold to determine a vehiclestability error, if the result is negative method 900 absorbs torquefrom the driveline via the electric machine (e.g., 120 of FIG. 1A)during the inertia phase of the upshift (e.g., inertia phase is aportion of the upshift where engine speed is synchronized to speed of anon-coming gear or gear being engaged) to reduce the vehicle stabilityerror to zero or a positive value. For example, the vehicle stabilityerror may be input into a proportional/integral controller which outputsan amount of torque to absorb from the driveline. However, the amount oftorque absorbed from the driveline may be limited by battery or electricmachine characteristics or conditions. If the electric machine lackscapacity to absorb torque from the driveline sufficient to provide zeroor less than zero vehicle stability error, then additional drivelinetorque reductions may be provided at 970. The vehicle stability metricmay be determined a plurality of times during the course of the upshiftso that electric machine torque may be revised a plurality of timesduring the upshift. In this way, driveline torque may be feedbackcontrolled based on the vehicle stability metric in real-time.

In a second example, method 900 may absorb driveline torque during theinertia phase of the transmission gear upshift based on empiricallydetermined values stored in memory. For example, if the vehiclestability metric is at or greater than the vehicle stability threshold,the electric machine may absorb an empirically determined amount oftorque from the driveline during the upshift inertia phase to reducedriveline torque disturbances and the possibility of further degradingvehicle stability.

In a third example, method 900 may begin reducing driveline torque viathe electric machine during the inertia phase of an upshift in responseto the vehicle stability metric exceeding a first empirically determinedthreshold and the amount of driveline torque absorbed by the electricmachine may increase such that the vehicle stability metric may increaseup to, but not exceed, a value of a second empirically determinedthreshold. In this way, the vehicle may operate at or below the secondvehicle stability threshold or limit. Method 900 proceeds to 970.

At 970, method 900 may truncate engine torque via retarding engine sparktiming and/or increase a duration (e.g., amount of time from start ofupshift to end of upshift) of the upshift and increase a duration ofclutch slip during the inertia phase of the upshift for torque that isnot absorbed in the inertia phase of the upshift by the electricmachine. In one example, method 900 reduces driveline torque at thetransmission output shaft via retarding engine spark timing orincreasing the upshift duration and slip of the on-coming clutch (e.g.,clutch that supplies torque to the new gear being engaged) that is notabsorbed via the electric machine and that could cause the vehiclestability metric to exceed the vehicle stability threshold.Alternatively, method 900 reduces driveline torque at the transmissionoutput shaft via increasing engine spark retard or increasing theduration of the upshift so that the vehicle stability metric may bereduced to a value less than the vehicle stability threshold. Further,the amount of driveline torque reduction provide by the engine may bedetermined based on, or as a function of, a value of the vehiclestability metric. Likewise, an amount of time upshift duration isincreased may be made responsive to, or a function of, a value of thevehicle stability metric.

In one example, if the vehicle stability metric is approaching thevehicle stability threshold, the duration of the upshift increases untilthe vehicle stability metric reaches the vehicle stability threshold,then engine spark timing is retarded. This may allow vehicle fuelefficiency to remain higher since engine torque is not truncated earlyon during the shift. Similarly, as the value of the vehicle stabilitymetric is reduced and move away from the value of the vehicle stabilitythreshold in a direction of increased vehicle stability, the amount ofspark retard may be decreased and the duration of the upshift may bereduced. If the value of the vehicle stability metric reaches or exceedsthe vehicle stability threshold, engine torque may be reduced to reducethe possibility of further degrading vehicle stability. Additionally,the clutch slip (e.g., difference in input speed and output speed of theclutch when the clutch is transferring torque) may be increased when thevehicle stability metric approaches the vehicle stability threshold tofurther reduce transmission output shaft torque. Clutch slip may beincreased via reducing pressure of fluid supplied to the clutch.Conversely, clutch slip may be decreased via increasing pressure offluid supplied to the clutch.

In another example, the upshift duration may be increased and enginespark timing may be retarded based on empirically determined valuesstored in a table or function that is indexed based on the a vehiclestability error and the amount of torque absorbed via the electricmachine. The table outputs a spark retard amount and a gear upshiftduration. Method 900 proceeds to 975.

At 975, method 900 describes an alternative method for determining theupshift duration. In particular, the upshift duration may be determinedas a function of driveline torque (e.g., transmission output shafttorque) during the inertia phase of the upshift, the vehicle stabilitythreshold, and clutch slip shift energy (e.g., an amount of energydissipated by the clutch during the shift which may be estimated bytorque input to the clutch and clutch input and output speeds). Forexample, a table or function may hold empirically determined upshiftdurations for each possible gear upshift (e.g., first to second gearupshift, second to third gear upshift, and third to fourth gear upshift)and the table or function may be indexed via the torque during theinertia phase, the vehicle stability threshold, and the clutch slipshift energy. The table or function outputs the upshift duration. Method900 proceeds to 980.

At 980, method 900 adjusts the transmission upshift duration, enginespark timing, and electric machine torque according to the upshiftduration, engine spark timing, and electric machine torque valuesdetermined at least one of steps 970, 975, 960, 950, and 955. Thetransmission upshift duration may be increased via decreasing a pressureof fluid applied to a clutch being applied to perform an upshift. Thereduced clutch pressure may increase clutch slippage so that theclutch's torque transfer capacity may be reduced, thereby lengtheningthe gear shift duration from the beginning of the gear shift to the endof the gear shift when the clutch transferring torque to the on-cominggear is fully locked. The clutch slip time (e.g., amount of time theclutch slips from when the clutch begins transferring torque to when theclutch is fully locked during a gear shift) may also increase whenpressure applied to a clutch is reduced during a gear shift.

At 945, method 900 judges if engine torque truncation via increasedspark timing is desired. Method 900 may judge if engine torquetruncation is desired via information from a user input, a vehicleoperating mode, or vehicle operating conditions. For example, enginetorque truncation may be desired if a human drive permits engine torquetruncation for the purpose increasing vehicle stability. Alternatively,method 900 may judge that engine torque truncation is desired inresponse to the vehicle being in a sport or performance mode. In stillanother example, method 900 may judge that engine torque truncation isdesired based on a magnitude of a vehicle stability error. If method 900judges that engine torque truncation is desired, the answer is yes andmethod 900 proceeds to 960. Otherwise, the answer is no and method 900proceeds to 950.

At 960, method 900 truncates engine torque via retarding engine sparktiming. In addition, method 900 may increase a duration of the upshiftand increase a duration of clutch slip (e.g., an amount of time betweenwhere clutch slip is present and when the clutch is locked) during theinertia phase of the upshift. In one example, method 900 reducesdriveline torque at the transmission output shaft via retarding enginespark timing or increasing the upshift duration and slip of theon-coming clutch (e.g., clutch that supplies torque to the new gearbeing engaged) that could cause the vehicle stability metric to exceedthe vehicle stability threshold. Alternatively, method 900 reducesdriveline torque at the transmission output shaft via increasing enginespark retard and/or increasing the duration of the upshift so that thevehicle stability metric may be reduced to a value less than the vehiclestability threshold. Further, the amount of driveline torque reductionprovided by the engine may be determined based on, or a function of, avalue of the vehicle stability metric. Likewise, an amount of timeupshift duration is increased may be made responsive to, or a functionof, a value of the vehicle stability metric.

In one example, if the vehicle stability metric is approaching thevehicle stability threshold, the duration of the upshift increases untilthe vehicle stability metric reaches the vehicle stability threshold,then engine spark timing is retarded. This may allow vehicle fuelefficiency to remain higher since engine torque is not truncated earlyon during the shift. Similarly, as the value of the vehicle stabilitymetric is reduced and move away from the value of the vehicle stabilitythreshold in a direction of increased vehicle stability, the amount ofspark retard may be decreased and the duration of the upshift may bereduced. If the value of the vehicle stability metric reaches or exceedsthe vehicle stability threshold, engine torque may be reduced to reducethe possibility of further degrading vehicle stability. Additionally,the clutch slip (e.g., difference in input speed and output speed of theclutch while the clutch is transferring torque) may be increased whenthe vehicle stability metric approaches the vehicle stability thresholdto further reduce transmission output shaft torque.

In another example, the engine spark timing may be retarded based onempirically determined values stored in a table or function that isindexed based on a vehicle stability error and the amount of torqueabsorbed via the electric machine. The table outputs a spark retardamount and duration of the upshift. In other example, the upshiftduration may be determined as described at 975. Method 900 proceeds to980.

At 950, method 900 lengthens the duration of the upshift based on torquein the portion of the inertia phase of the upshift that may increase thevalue of the vehicle stability metric to a value greater than thevehicle stability threshold. In one example, the shift duration isincreased as described at 955. In another example, method 900 mayincrease the upshift duration based on the extent that the vehiclestability metric exceeds a first empirically determined threshold suchthat the vehicle stability metric may increase up to, but not exceed, avalue of a second empirically determined threshold. In other words, theupshift duration may be progressively increased after the vehiclestability metric exceeds the first vehicle stability threshold value andso that it does not exceed the second vehicle stability threshold value.In this way, the vehicle may operate at or below a vehicle stabilitythreshold or limit. Method 900 proceeds to 955.

At 955, method 900 determines the upshift duration as a function ofdriveline torque (e.g., transmission output shaft torque) during theinertia phase of the upshift, the vehicle stability threshold, andclutch slip shift energy (e.g., an amount of energy dissipated by theclutch during the shift which may be estimated by torque input to theclutch and clutch input and output speeds). For example, a table orfunction may hold empirically determined upshift durations for eachpossible gear upshift (e.g., first to second gear upshift, second tothird gear upshift, and third to fourth gear upshift), and the table orfunction may be indexed via the torque during the inertia phase, thevehicle stability threshold, and the clutch slip shift energy. The tableor function outputs the upshift duration. Method 900 proceeds to 980.

In this way, the possibility of decreasing vehicle stability may bedecreased via increasing upshift duration, increasing engine sparkretard, increasing torque absorbed from a driveline via an electricmachine, and/or increased transmission clutch slip. Increasing the shiftduration reduces torque delivered to the transmission output shaft asdoes reducing engine torque via spark retard. The reduced transmissionoutput torque may provide additional vehicle stability. Further, vehiclestability may be improved via reducing wheel torque by absorbingtransmission output torque via an electric machine positioned downstreamof the transmission.

Referring now to FIG. 10, an exemplary hybrid driveline operatingsequence is shown. The sequence of FIG. 10 may be provided according tothe method of FIG. 9 along with or in conjunction with the system ofFIGS. 1A-4. The plots shown in FIG. 10 occur at the same time and arealigned in time.

The first plot from the top of FIG. 10 is a plot of a vehicle stabilitymetric versus time. The vertical axis represents a value of the vehiclestability metric and the value of the vehicle stability metric increasesin the direction of the vertical axis arrow. Higher values of thevehicle stability metric indicate decreased vehicle stability. Lowervehicle stability values indicate increased vehicle stability. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure. Horizontal line 1002represents a vehicle stability threshold value. Vehicle stability metricvalues above horizontal line 1002 may be less desirable.

The second plot from the top of FIG. 10 is a plot of a state of vehicleupshift request versus time. A vehicle upshift is requested when thetrace is at a higher level near the vertical axis arrow. A vehicleupshift is not requested when the trace is at a lower level near thehorizontal axis. The horizontal axis represents time and time increasesfrom the left side of the figure to the right side of the figure.

The third plot from the top of FIG. 10 is a plot of battery state ofcharge (SOC) versus time. The vertical axis represents battery SOC andSOC increases in the direction of the vertical axis arrow. SOC is a lowvalue at the horizontal axis. The horizontal axis represents time andtime increases from the left side of the figure to the right side of thefigure. Horizontal line 1004 represents a SOC threshold. If battery SOCis greater than the level of horizontal line 1004, the battery orelectric energy storage device does not accept charge from the electricmachine. The battery or electric energy storage device accepts chargewhen the trace is less than or at a lower level than threshold 1004.

The fourth plot from the top of FIG. 10 is a plot of upshift duration(e.g., amount of time from start of upshift to the end of the upshift)versus time. The vertical axis represents the duration of the upshiftand the duration of the upshift increases in the direction of thevertical axis arrow. The horizontal axis time and time increases fromthe left side of the figure to the right side of the figure.

The fifth plot from the top of FIG. 10 is a plot of engine spark retardversus time. The vertical axis represents engine spark retard and enginespark retard increases in the direction of the vertical axis arrow. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

The sixth plot from the top of FIG. 10 is a plot of negative electricmachine torque (e.g., torque absorbed by the electric machine (e.g., 120of FIG. 1A) when the electric machine is operating a generator oralternator mode) versus time. The vertical axis represents electricmachine negative and the magnitude of the negative electric machinetorque increases in the direction of the vertical axis arrow. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

At time T20, the value of the vehicle stability metric is less thanthreshold 1002 and a transmission upshift is not requested as indicatedby the upshift request trace being at a lower level. The transmissionupshift duration is a small value since no transmission upshift isrequested. Engine spark is not retarded since the engine spark retardtrace is at a lower level. The electric machine negative torque is at alower level indicating that the electric machine is not absorbing torquefrom the hybrid vehicle driveline.

Between time T20 and time T21, the vehicle stability metric valueincreases to indicate decreasing vehicle stability. The vehiclestability metric may increase as a vehicle enters a corner of a road ortrack. Transmission upshifting is not requested and battery state ofcharge is at a higher level above threshold 1004. The battery does notaccept charge when battery SOC is at the level shown. A transmissionupshift is not requested and the shift duration is a small value.

At time T21, a transmission upshift is requested. The transmissionupshift may be requested in response to a transmission shift schedule,vehicle speed, and a desired torque. The battery SOC remains abovethreshold 1004 so the electrical machine negative torque is zero inresponse to the requested upshift. However, the shift duration isincreased to a longer duration (e.g., longer period of time) in responseto the upshift request and vehicle stability being at threshold 1002. Byincreasing the shift duration, driveline torque disturbances that mayoccur during an inertia phase of an upshift may be reduced so thattorque at the vehicle wheels may be reduced as compared to if theupshift duration where shorter. In addition, engine spark retard isincreased so that spark timing is retarded away from minimum sparktiming for best engine torque. Retarding the engine spark timing reducesengine torque, but it may reduce engine fuel economy. The engine sparkretard is at a higher level to indicate engine torque is reduced via alarger amount of spark retard. Increasing the shift duration and theengine spark retard may reduce the possibility of the vehicle stabilitymetric exceeding threshold 1002.

Between time T21 and time T22, an upshift is performed in response tothe upshift request and the upshift is performed with a longer upshiftduration and reduced engine torque. The vehicle stability metric isreduced as time approaches time T22. The vehicle stability metric may bereduced as a vehicle exits a corner of a road or track.

At time T22, a second transmission upshift is requested in response tovehicle conditions including the transmission shift schedule, vehiclespeed, and requested torque. The vehicle stability metric is at a lowerlevel to indicate that the vehicle is operating in stable conditions.The battery SOC remains above threshold 1004. Therefore, the shiftduration is made short and the amount of spark retard is zero so thatdriveline torque is not reduced responsive to the vehicle stabilitymetric. In addition, driveline torque absorbed by the electric machineis substantially zero.

Between time T22 and time T23, an upshift is performed in response tothe upshift request and the upshift is performed with a shorter upshiftduration and at requested engine torque. The vehicle stability metric isincreases as time approaches time T23. The battery SOC is reduced to alevel less than threshold 1002 as charge is consumed via the electricmachine.

At time T23, a transmission upshift is requested. The battery SOC is nowbelow threshold 1004 so the electrical machine may absorb torque fromthe driveline. The amount of negative torque being absorbed from thedriveline is increased since the SOC value is lower. By deliveringtorque to the electric machine, the torque may be converted intoelectrical energy that is stored in the battery or electric energystorage device. In this example, the electric machine's capacity tostore charge during the upshift is less than the amount of energyprovided during the upshift so engine torque is reduced to further lowerdriveline torque. The spark retard at time T23 is much less than theamount of spark retard used at time T21 to reduce driveline torque. Theshift duration is short so that clutch wear may be reduced. Suchdriveline operation may be provided when the vehicle is operating in anon-sport mode, such as a touring mode, where vehicle performance isreduced as compared to when the vehicle is operated in a sport mode.

Between time T23 and time T24, an upshift is performed in response tothe upshift request and the upshift is performed with a shorter upshiftduration and at requested engine torque. The vehicle stability metric isincreases as time approaches time T23.

At time T24, another transmission upshift is requested. The battery SOCremains below threshold 1004 so the electrical machine may absorb torquefrom the driveline and convert the torque into electrical energy that isstored in the battery or electric energy storage device. In thisexample, the electric machine's capacity to store charge during theupshift is less than the amount of energy provided during the upshift sodriveline torque at the vehicle wheels is reduced via increasing aduration of the upshift. Nevertheless, the amount of torque absorbed bythe electric machine is a higher level. Engine spark is not retarded attime T24 so that engine torque is available quickly. Such drivelineoperation may be provided when the vehicle is operating in a sport mode,such as a sport mode, where vehicle performance is increased as comparedto when the vehicle is operated in a touring mode.

Thus, vehicle stability may be improved in different ways duringdifferent vehicle operating conditions. For example, vehicle stabilitymay be improved via increasing upshift duration so that less torque maybe provided to vehicle wheels while vehicle stability is decreasing. Inaddition, transmission output torque may be absorbed via an electricmachine or reduced via engine spark retard in response to lower vehiclestability. By reducing wheel torque, the possibility of furtherdecreasing vehicle stability may be reduced. Further, driveline torquedisturbances that may occur due to shifting may be reduced to improvevehicle drivability. In some examples, the vehicle stability may beadjusted via shift duration, engine torque, and electric machine torqueso that vehicle stability may approach, but not exceed, a vehiclestability threshold or limit.

Referring now to FIGS. 11 and 12, a method for adapting clutches of atransmission is shown. The method of FIGS. 11 and 12 may be incorporatedinto the system of FIGS. 1A-4 as executable instructions stored innon-transitory memory of one or more controllers. Additionally, portionsof the method of FIGS. 11 and 12 may be actions performed via thecontrollers shown in FIGS. 1A-4 to transform a state of a device oractuator in the real world. The method shown in FIGS. 11 and 12 mayoperate in conjunction and cooperation with other methods describedherein. The method of FIGS. 11 and 12 may be applied to adapt transferfunctions of clutches 126 and 127 shown in FIG. 4.

At 1105, method 1100 judges if the engine is to be connected to thewheels to satisfy vehicle operating requirements. For example, theengine may be connected to the wheels if a desired or driver demandedwheel torque is greater than a threshold level. However, the engine maybe decoupled from the wheels if the desired or driver demanded wheeltorque is less than the threshold level. If method 1100 judges that theengine is to be connected to the wheels to satisfy vehicle operatingrequirements, the answer is yes and method 1100 proceeds to 1135.Otherwise, the answer is no and method 1100 proceeds to 1110.

At 1110, method 1100 judges if clutch adaptation is desired. Clutchadaptation may be desired after the vehicle has been driven a thresholddistance. Further, clutch adaptation may be desired if the vehicledriveline accelerates or decelerates more or less than is desired whilethe clutch is being closed. In other instances, clutch adaptation may bedesired if the vehicle in which the clutch operates has not been drivenfor an extended period of time. If method 1100 judges that clutchadaptation is desired, the answer is yes and method 1100 proceeds to1115. Otherwise, the answer is no and method 1100 proceeds to 1135.

At 1115, method 1100 judges if the hybrid vehicle driveline is operatingin a series mode. Method 1100 may judge that the hybrid vehicledriveline is operating in a series mode when the engine is running andcombusting fuel with clutches of the transmission open. Further, torquefrom an electric machine (e.g., 120) may be propelling the vehicle thatincludes the engine. Sensors (e.g., synchronizer position sensors)within the transmission may indicate the position of transmissionclutches. If method 1100 judges that the hybrid vehicle driveline isoperating in a series mode, the answer is yes and method 1100 proceedsto 1120. Otherwise, the answer is no and method 1100 proceeds to 1140.

At 1140, method 1100 judges if the hybrid driveline is operating in anelectric only propulsion mode or electric vehicle mode. Method 1100 mayjudge that the hybrid driveline is operating in an electric onlypropulsion mode if the engine is stopped rotating (e.g., not combustingair and fuel) and an electric machine positioned in the driveline isproviding torque to propel or slow the vehicle. If method 1100 judgesthat the hybrid driveline is operating in an electric only propulsionmode, the answer is yes and method 1100 proceeds to 1145. Otherwise, theanswer is no and method 1100 proceeds to 1150.

At 1145, method 1100 starts the engine and accelerates the engine to adesired speed (e.g., a speed within a threshold speed above or below aspeed of the transmission input shaft speed that is rotating at a higherspeed of the two transmission input shaft speeds). Alternatively, enginespeed may accelerate to engine idle speed. The engine is operated in aspeed control mode to achieve the desired engine speed. Method 1100proceeds to 1120.

At 1150, method 1100 judges whether or not the hybrid driveline isoperating in a parallel mode. Method 1100 may judge that the hybriddriveline is operating in a parallel mode when the engine is coupled tothe vehicle wheels through a closed clutch. Further, the electricmachine (e.g., 120) may be providing torque to the driveline. If method1150 judges that the hybrid driveline is operating in a parallel mode,the answer is yes and method 1100 proceeds to 1155. Otherwise, theanswer is not and method 1100 returns to 1115.

At 1155, method 1100 adjusts torque input to the transmission tosubstantially zero torque (e.g., +10 N-m). Torque input to thetransmission may be adjusted via adjusting engine torque or adjustingtorque of the electric machine positioned downstream of thetransmission. Engine torque may be adjusted via adjusting a position ofa throttle or other torque actuator. Method 1100 proceeds to 1160.

At 1160, method 1100 opens transmission clutches to decouple the enginefrom the vehicle wheels. The transmission clutches are opened so that notorque is transferred across the clutches. Method 1100 proceeds to 1120.

At 1120, method 1100 selects which clutch is to be adapted. In oneexample, method 1100 first selects the first clutch (e.g., 126). Afterthe first clutch is adapted, then the second clutch (e.g., 127) isadapted. However, in other examples, the clutch selected to be adaptedis a clutch that provides a torque transfer capacity that is differentthan may be expected. Method 1100 proceeds to 1125 after the clutch tobe adapted is selected.

At 1125, method 1100 adapts the selected clutch according to the methodof FIG. 12. In particular, a transfer function that describes operationof the clutch may be adapted to improve clutch engagement anddisengagement. The vehicle may be traveling on a road and be propelledsolely from torque provided by the electric machine positioneddownstream of the transmission when clutch adaptation is performed.Method 1100 proceeds to 1130 after adapting the selected clutch.

At 1130, method 1100 judges if adaptation of other clutches is desired.Alternatively, the same clutch may be adapted a second time to confirmthe adaptation process. If method 1100 judges that additional clutchadaptation is desired, the answer is yes and method 1100 returns to1115. Otherwise, the answer is no and method 1100 proceeds to 1135.

At 1135, method 1100 operates the hybrid driveline according to adesired mode and adapted transfer functions for transmission clutches.The desired hybrid mode may be based on driver demanded wheel torque,battery SOC, and other vehicle operating conditions. The hybriddriveline may operate in electric only mode, series hybrid vehicle mode,and parallel hybrid vehicle mode. If the hybrid driveline is operated inelectric vehicle only mode in response to vehicle operating conditions,engine rotation is stopped and the engine ceases combusting fuel andair. If the hybrid driveline is operated in series mode in response tovehicle operating conditions, the engine continues combusting fuel andair and the transmission clutches are open. If the hybrid driveline isoperated in a parallel mode in response to vehicle operating conditions,the engine speed is controlled to a synchronous speed with one of thetransmission input shafts and a transmission clutch is closed. Method1100 proceeds to exit after the hybrid driveline is operating in adesired mode responsive the vehicle operating conditions.

Referring now to FIG. 12, method 1200 optionally shifts the transmissioninto a tallest gear or the gear with the highest gear number at 1205.For example, if the transmission is a six speed transmission, method1200 may shift the gear into sixth gear. The transmission may be shiftedinto gear by repositioning transmission shifting forks. Method 1200proceeds to 1210.

At 1210, method 1200 controls engine speed to provide a desired speeddifference between a desired speed of the transmission input shaftconnected to the clutch being adapted and engine speed. The engine isoperated in a speed control mode. In speed control mode, engine speedfollows a desired speed, which may be constant or varying, while enginetorque is varied to achieve the desired engine speed. Engine speed maybe controlled to a speed above or below the desired speed of thetransmission input shaft. In some examples, the desired transmissioninput shaft speed may be a function of the engaged gear and vehiclespeed. Also, torque of an integrated starter/generator coupled to theengine may be adjusted to zero. Method 1200 proceeds to 1215.

At 1215, method 1200 optionally moves the engine from speed control modeto a torque control mode. In torque control mode, the engine torquefollows a desired torque while engine speed is allowed to vary. In oneexample, engine torque is commanded to a torque that maintains enginespeed at the desired speed mentioned at 1210. If the engine is commandedto a torque control mode, the integrated starter/generator is commandedto a speed control mode. Integrated starter/generator speed and enginespeed are controlled to a speed above or below a speed of a transmissioninput shaft coupled to the clutch that is being adapted. Method 1200proceeds to 1220.

At 1220, method 1200 increases and then decrease torque capacity of theclutch selected to be adapted by adjusting a clutch torque capacitycommand. The clutch torque capacity command may be converted into aclutch application pressure (e.g., a pressure of fluid supplied to theclutch). The clutch application pressure may then be converted into acommand to adjust a pressure control valve or a pump as discussed inFIG. 13. Further, method 1200 determines actual pressure of fluidsupplied to the clutch to adjust the torque capacity of the clutch. Theclutch torque capacity is an amount of torque the clutch may transferfrom the input side of the clutch to the output side of the clutch orvice-versa. The clutch torque capacity may be increased from a smallvalue to a large value and the decreased from the large value to thesmall value. Method 1200 proceeds to 1225.

At 1225, method 1200 adjusts torque of the engine and/or the integratedstarter/generator to compensate for adjusting the clutch torquecapacity. The engine torque and/or integrated starter/generator torqueare adjusted simultaneously as the clutch torque capacity is adjusted.The engine and/or integrated starter/generator torque are adjusted asdiscussed in FIGS. 14A and 14B so that speed of the transmission inputshaft coupled to the clutch being adapted is maintained at a speed thatis based on vehicle speed and the engaged transmission gear. Forexample, if the engine is in a torque control mode and providing aconstant amount of torque, torque of the integrated starter/generator isadjusted to maintain engine and motor speed at the desired engine speed.If the engine is in a speed control mode and integratedstarter/generator torque is zero or a constant value, engine torque isadjusted to maintain engine speed at the desired engine speed. Method1200 proceeds to 1230.

At 1230, method 1200 adjusts torque of the electric machine positioneddownstream of the transmission (e.g., 125) to maintain a desired wheeltorque. The electric machine torque is adjusted responsive to the torquetransferred via the clutch being adapted, and the torque transferred viathe clutch being adapted may be estimated based on the change in enginetorque or the change in integrated starter/generator torque. Forexample, if engine torque or integrated starter/generator torque isincreased to maintain engine speed, torque of the electric machinepositioned downstream of the transmission is decreased by acorresponding amount to compensate for torque transferred from theengine to the transmission input shaft via the clutch. Similarly, ifengine torque or integrated starter/generator torque is decreased tomaintain engine speed, torque of the electric machine positioneddownstream of the transmission is increased by a corresponding amount tocompensate for torque transferred from the transmission input shaft tothe engine via the clutch. The electric machine torque is adjusted whilethe clutch is being applied and released and while engine and integratedstarter/generator torque is adjusted. Method 1200 proceeds 1235.

At 1235, method 1200 stores values of clutch pressures and change inengine and/or integrated starter generator torque measured duringapplication and release of the clutch for the commanded clutch torquecapacities to controller memory. Method 1200 proceeds to 1240.

At 1240, method 1200 adjusts clutch transfer function values thatdescribe the relationship between clutch fluid application pressure andtorque change of the engine and/or integrated starter generator. Thetorque change of the engine and/or the integrated starter generator isan estimate of the clutch torque capacity. In one example, the valuesare stored in a table or function that may be described as a transferfunction that relates clutch fluid application pressure (e.g., pressureof fluid supplied to the clutch being adapted) to clutch torquecapacity. The old values in the transfer function may be replaced by newvalues or the transfer function may be revised based on an average ofthe old values and the new values. Method 1200 proceeds to 1245.

At 1245, method 1200 fully opens the clutch being adapted. Method 1200proceeds to exit after the clutch being adapted is opened.

Referring now to FIG. 13, a block diagram showing a transfer functionand how it may be applied to control a clutch is shown. A requestedclutch torque transfer capacity 1305 is used to index transfer function1310. The requested torque transfer capacity (e.g., an amount of torquea clutch may transfer from its input to its output) may originate froman empirically determined clutch application profile stored in memory orfrom an analytical solution. Transfer function 1310 describes arelationship between a torque transfer capacity and a pressure appliedto the clutch to provide the torque transfer capacity. The relationshipmay be described by a curve or a series of points that may beinterpolated between. The transfer function may be adapted by replacinginaccurate values of the transfer function with more accurate values.For example, as described elsewhere herein torque transferred across theclutch may be estimated via determining an amount of torque provided bya motor to hold one side of the clutch at a steady substantiallyconstant (e.g., ±50 RPM) speed while the clutch is closed and clutchpressure is monitored. In particular, for a given clutch pressure, themotor outputs a torque, which may be determined from motor current, tohold the clutch at a steady substantially constant speed. The torqueestimate from the motor may replace a torque value in transfer function1310 that corresponds to the clutch application pressure that resultedin the torque value determined from the motor. The output of transferfunction 1310 is input to a second transfer function 1315.

Transfer function 1315 converts the pressure output from transferfunction 1310 to a duty cycle or other valve position command. The valveposition command is output to valve 1320. Valve 1320 controls a supplyof fluid to clutch 126 shown in FIG. 4. Transmission pump 412 suppliesfluid from transmission sump 411 to pressure control valve 1320. Itshould be noted that in some examples, the clutch torque transfercapacity may be converted directly into a valve command via a singletransfer function. Such a transfer function may be adapted in a similarway. Hydraulic fluid is supplied to clutch 127 via a similar systemhaving similar components and a similar configuration. Transmission pump412 may be electrically or engine driven.

Turning to FIG. 14A, an example timeline 1400 is shown for conducting aclutch adaptation operation, according to methods 1100 and 1200described herein, and as applied to the systems described herein andwith reference to FIGS. 1A-4. Timeline 1400 includes plot 1405,indicating engine speed, over time. Line 1410 represents transmissioninput shaft (e.g. 402, 404) speed to a dual clutch transmission (e.g.125). Timeline 1400 further includes plot 1415, indicating a clutchpressure, over time, where clutch pressure may range from a higherpressure that closes (e.g. locked) the clutch, to a lower pressure thatopens (e.g. completely unlocked) the clutch, over time. Timeline 1400further includes plot 1420, indicating an integrated starter/generator(ISG) (e.g. 142) torque, over time. Alternatively, engine torque may becontrolled similarly.

In the following description, it may be understood that the dual clutchtransmission in which the clutch adaptation operation is being performedmay include a first clutch (e.g. 126), and a second clutch (e.g. 127).Furthermore, it may be understood that the dual clutch transmission mayinclude a first input shaft (e.g. 402), and a second input shaft (e.g.404). The clutch adaptation operation may be conducted on either thefirst clutch, where input shaft speed illustrated in FIG. 14A maycorrespond to the first input shaft, or on the second clutch, whereinput shaft speed illustrated in FIG. 14A may correspond to the secondinput shaft. For simplicity, a single clutch pressure and a single inputshaft speed is indicated, thus it may be understood that the clutchadaptation operation is being performed on one clutch, where the inputshaft speed thus corresponds to that one clutch. For clarity, the clutchbeing adapted in example timeline 1400 may be understood to be firstclutch (e.g. 126), where the input shaft speed corresponds to the firstinput shaft (e.g. 402).

At time T25, the engine is rotating at a constant speed. The firstclutch is closed, thus engine torque is being transmitted to vehiclewheels via the first clutch, to a vehicle driveline, through the firstinput shaft. ISG torque is slightly negative, thus the ISG is operatingin a generator mode of operation. Thus, it may be understood that attime T25 the vehicle is being operated in a parallel mode of hybridelectric vehicle operation.

At time T26, first clutch pressure is reduced to 0, thus opening theclutch. Responsive to the opening of the clutch, it may be understoodthat the vehicle may be operating in a series mode of hybrid electricvehicle operation. Between time T26 and T27, engine speed is reduced tobelow the first input shaft speed. The engine speed is reduced viareducing engine torque and increasing the amount of negative torqueapplied to the engine for a duration of time, via the ISG, before thenegative torque applied to the engine is returned to the initialnegative torque. In other words, the load on the engine is increased viathe ISG for a duration between time T26 and T27, before returning to theinitial ISG-determined load.

At time T27, first clutch pressure is raised to above zero, but below atouchpoint where clutch capacity may be measurable. The amount by whichthe clutch pressure is raised above zero at time T27 may in someexamples be a function of part-to-part variability and change overtime).

Between time T27 and T28, first clutch pressure is slowly increased, orraised up. At time T28, the first clutch begins to carry capacity, wherecarrying capacity may refer to the engine being coupled to a measurableamount to the first input shaft, via the first clutch. In other words,the torque capacity of the first clutch is increased. Negative ISGtorque is increased to regulate engine speed in the presence ofincreasing clutch capacity. Engine torque may be kept constant toimprove accuracy of the torque change measurement. In other words, sinceincreasing torque capacity of the clutch tends to increase torque at theengine due to the first input shaft speed being greater than enginespeed, excess torque that would accelerate the engine may instead beabsorbed by the ISG to maintain engine speed constant. As such, betweentime T28 and T29, while clutch capacity is increased, magnitude ofnegative ISG torque increases accordingly.

Between time T29 and T30, clutch pressure is held constant, and as such,negative ISG torque is indicated to be constant. In other words, aconstant amount of excess torque resulting from the difference in inputshaft speed and engine speed may be absorbed by the ISG operating in theregenerative mode.

At time T30, first clutch pressure begins to be decreased. Between timeT30 and T31, while clutch capacity is decreased, excess torque due toinput shaft speed being greater than engine speed becomes less and less,as the first input shaft becomes decoupled from the engine.

At time T31, clutch pressure reduces to a point of no measurable clutchcapacity. The point at which clutch pressure reaches no measurableclutch capacity may be the same as the clutch pressure indicated at timeT27, for example. Between time T31 and T32, clutch pressure is furtherreduced, and at time T32 clutch pressure reduces to zero, thus fullyopening the first clutch.

Between time T32 and T33, engine speed is controlled to match thedesired input shaft speed by operating the engine in a speed controlmode, responsive to a desired return to parallel hybrid electric vehicleoperation, as discussed above. At time T33, responsive to engine speedmatching the first input shaft speed, the first clutch may be closed toconnect the engine to the first input shaft.

Turning now to FIG. 14B, an example timeline 1450 is shown forconducting a clutch adaptation operation, according to methods 1100 and1200 described herein, and as applied to the systems described hereinand with reference to FIGS. 1A-4. Timeline 1450 includes plot 1455,indicating engine speed, over time. Line 1460 represents transmissioninput shaft (e.g. 402, 404) speed to a dual clutch transmission (e.g.125). Timeline 1450 further includes plot 1465, indicating a clutchpressure, over time, where clutch pressure may range from closed (e.g.locked), or open (e.g. completely unlocked), over time. Timeline 1450further includes plot 1470, indicating an integrated starter/generator(ISG) (e.g. 142) torque, over time. Timeline 1450 is essentially thesame as FIG. 14A, except that instead of engine speed being controlledto below input shaft speed, engine speed is controlled to above inputshaft speed. Aspects of timeline 1450 that are different from timeline1400 as a result of controlling engine speed to be above input shaftspeed will be discussed in the description below, accordingly.

In the following description, similar to that described above for FIG.14A, it may be understood that the dual clutch transmission in which theclutch adaptation operation is being performed may include a firstclutch (e.g. 126), and a second clutch (e.g. 127). Furthermore, it maybe understood that the dual clutch transmission may include a firstinput shaft (e.g. 402), and a second input shaft (e.g. 404). The clutchadaptation operation may be conducted on either the first clutch, whereinput shaft speed illustrated in FIG. 14B may correspond to the firstinput shaft, or on the second clutch, where input shaft speedillustrated in FIG. 14B may correspond to the second input shaft. Forsimplicity, a single clutch pressure and a single input shaft speed isindicated, thus it may be understood that the clutch adaptationoperation is being performed on one clutch, where the input shaft speedthus corresponds to that one clutch. For clarity, the clutch beingadapted in example timeline 1450 may be understood to be first clutch(e.g. 126), where the input shaft speed corresponds to the first inputshaft (e.g. 402).

At time T25 b, the engine is rotating at a constant speed. The firstclutch is closed, thus engine torque is being transmitted to vehiclewheels via the first clutch, to a vehicle driveline, through the firstinput shaft. ISG torque is slightly negative, thus the ISG is operatingin a generator mode of operation. Thus, it may be understood that attime T25 b the vehicle is being operated in a parallel mode of hybridelectric vehicle operation.

At time T26 b, first clutch pressure is reduced to 0, thus opening theclutch. Responsive to the opening of the clutch, it may be understoodthat the vehicle may be operating in a series mode of hybrid electricvehicle operation. Between time T26 b and T27 b, engine speed isincreased to above the first input shaft speed. The engine speed isincreased via increasing the amount of torque (positive torque) appliedto the engine for a duration of time, via the ISG, before the torqueapplied to the engine is returned to the initial negative torque. Inother words, the ISG may provide an increased torque to the engine inorder to raise engine speed above input shaft speed between time T26 band T27 b. Additionally, engine may be in a speed control mode whereengine torque is increased to increase engine speed to the desiredengine speed.

At time T27 b, first clutch pressure is raised to above zero, but belowa touchpoint where clutch capacity may be measurable. The amount bywhich the clutch pressure is raised above zero at time T27 b may in someexamples be a function of part-to-part variability and change overtime).

Between time T27 b and T28 b, first clutch pressure is slowly increased,or raised up. At time T28 b, the first clutch begins to carry capacity,where carrying capacity may refer to the engine being coupled to ameasurable amount to the first input shaft, via the first clutch. ISGtorque provided to the engine (positive torque) is increased to regulateengine speed in the presence of clutch capacity increasing. Enginetorque may be kept constant to improve accuracy of the torque changemeasurement. In other words, since increasing torque capacity of theclutch tends to decrease torque at the engine due to the first inputshaft speed being lower than engine speed, a torque deficit that woulddecelerate the engine may instead by filled in by increasing ISG torqueto maintain engine speed constant. As such, between time T28 b and T29b, while clutch capacity is increased, positive ISG torque increasesaccordingly.

Between time T29 b and T30 b, clutch pressure is held constant, and assuch, positive torque applied to the engine via the ISG is indicated tobe constant. In other words, engine torque is maintained constant eventhough input shaft speed is below engine speed, via positive torqueapplied to the engine via the ISG.

At time T30 b, first clutch pressure begins to be decreased. Betweentime T30 b and T31 b, while clutch capacity is decreased, the torquedeficit due to input shaft speed being less than engine speed becomesless and less, as the first input shaft becomes decoupled from theengine.

At time T31 b, clutch pressure reduces to a point of no measurableclutch capacity. The point at which clutch pressure reaches nomeasurable clutch capacity may be the same as the clutch pressureindicated at time T27 b, for example. Between time T31 b and T32 b,clutch pressure is further reduced, and at time T32 b clutch pressurereduces to zero, thus fully opening the first clutch.

Between time T32 b and T33 b, engine speed is controlled to match thedesired input shaft speed by operating the engine in a speed controlmode, responsive to a desired return to parallel hybrid electric vehicleoperation, as discussed above. At time T33 b, responsive to engine speedmatching the first input shaft speed, the first clutch may be closed toconnect the engine to the first input shaft.

Referring to the example timelines illustrated in FIGS. 14A-14B, bothtimelines depicted conditions wherein the vehicle system was operatingat least in part via the engine prior to the clutch adaptationprocedure, and furthermore, subsequent to the clutch adaptationprocedure, the vehicle system was indicated to return to operating atleast in part via the engine. However, in some examples, the vehiclesystem may be operating in an electric-only mode, for example wherein anelectric machine (e.g. 120) is solely propelling the vehicle. In such acondition, prior to conducting the clutch adaptation procedure theengine may be first started (with clutches open). Responsive to theengine start, engine speed may be controlled to either below input shaftspeed (as discussed with regard to FIG. 14A), or above input shaft speed(as discussed with regard to FIG. 14B). With the engine started, theclutch adaptation procedure may be carried out as described, withoutmodification. After completion of the clutch adaptation procedure,rather than returning to a mode of vehicle operation where the vehicleis propelled at least in part by the engine, as illustrated in FIGS.14A-14B, an engine shutdown may be carried out, such that the engine maybe propelled solely via power from the electric machine, as discussedabove.

Referring now to FIG. 15, a flowchart of a method for operating adriveline of a hybrid vehicle powertrain 100 is shown. The method ofFIG. 15 may be incorporated into the system of FIGS. 1A-4 as executableinstructions stored in non-transitory memory of one or more controllers.Additionally, portions of the method of FIG. 15 may be actions performedvia the controllers shown in FIGS. 1A-4 to transform a state of a deviceor actuator in the real world. The method shown in FIG. 15 may operatein conjunction and cooperation with other methods described herein.

At 1505, method 1500 determines vehicle operating conditions. Vehicleoperating conditions may include but are not limited to gear actuatorposition, vehicle speed, presently engaged gear, vehicle speed, engineoperating conditions, requested wheel torque, and electric machineoperating conditions. The vehicle operating conditions may becommunicated to a transmission controller via a vehicle systemcontroller or other controllers in the vehicle. Method 1500 proceeds to1510.

At 1510, method 1500 judges if the vehicle is in an electrical onlypropulsion mode. The vehicle is propelled solely via torque produced byan electric machine during electric only propulsion mode. In oneexample, method 1500 may judge that the vehicle is in an electric onlypropulsion mode if engine speed is zero and the electric machine (e.g.,120 of FIG. 1A) is providing torque to propel the vehicle. The engine isnot combusting air and fuel. Further, both clutches of dual clutchtransmission (e.g., 125) are in an open state. In other examples, avalue of a bit or byte in memory may provide an indication of vehiclemode. If method 1500 judges that the vehicle is in electric onlypropulsion mode, the answer is yes and method 1500 proceeds to 1515.Otherwise, the answer is no and method 1500 proceeds to exit.

At 1515, method 1500 determines conditions for shifting the transmissionwhile the vehicle is in electric only propulsion mode. In one example,the shifting conditions are empirically determined and saved in a shiftschedule that is stored in controller memory. The shift scheduleindicates when upshift and downshifts are requested. In one example,upshifts and downshifts may be scheduled in response to vehicle speedand desired wheel torque. For example, the transmission may upshift fromfirst gear to second gear at a vehicle speed of 5 KPH when demandedwheel torque is 10 N-m. Method 1500 proceeds to 1520.

At 1520, method 1500 judges if a transmission shift is requested. Method1500 may make the judgement based on values stored in the transmissionshift schedule described at 1515. If method 1500 judges that atransmission shift is requested, the answer is yes and method 1500proceeds to 1525. Otherwise, the answer is no and method 1500 proceedsto exit.

At 1525, method 1500 predicts or determines in real-time torque toaccelerate transmission components according to the on-coming gear(e.g., the gear being shifted into or being engaged). The prediction ordetermination of torque to accelerate transmission components may beprovided as described in FIGS. 16A-16D. In one example, torque toaccelerate the transmission components may be determined via thefollowing equation:compensation_tq=(estimated_synchro_tq)(gear_ratio)where compensation_tq is the torque to accelerate the transmissioncomponents, estimated_synchro_tq is estimated synchronizer torque, andgear_ratio is the ratio of the gear engaged between the electric machine(e.g., 120) and the synchronizer engaging the on-coming gear during theshift. This equation may be applied when the synchronizer torque isknown. If the synchronizer torque is not known, the following equationsmay be applied in some examples:estimated_input_acc=(input_speed−last_input_speed)/(sample_time)estimated_synchro_tq=(estimated_input_acc)(known_input_inertia)compensation_tq=(estimated_synchro_tq)(gear_ratio)where estimated_input_acc is estimated transmission input shaftacceleration, input_speed is present transmission input shaft speed,last_input_speed is last previous transmission input shaft speed,sample_time is transmission input shaft sample time,estimated_synchro_tq is estimated synchronizer torque,known_input_inertia is the known inertia of the transmission components,compensation_tq is the torque to accelerate the transmission components,and gear_ratio is the ratio of the gear engaged between the electricmachine (e.g., 120) and the synchronizer engaging the on-coming gearduring the shift. This equation may be applied when the synchronizertorque is unknown. Method 1500 proceeds to 1530 after determining thetorque to accelerate transmission components while the transmission isbeing shifted and the vehicle is in electric only propulsion mode.

At 1530, method 1500 communicates torque to accelerate transmissioncomponents from a transmission controller (e.g., 354 in FIG. 3) to othervehicle controllers (e.g., electric machine controller 352 in FIG. 3).Alternatively, vehicle system controller (e.g., 12 of FIG. 3) maycommunicate the torque to accelerate transmission components to theelectric machine controller. The torque to accelerate transmissioncomponents is applied by the electric machine controller to compensatethe torque to accelerate various transmission components (e.g.,layshafts, gears, output sides of clutches, etc.) to wheel speedfactoring in axle gearing and any other gearing between the transmissionoutput shaft and the vehicle wheels. For example, if the shiftaccelerates transmission components to a higher speed, a higher torqueis commanded of the electric machine so that vehicle speed is notreduced and a torque disturbance due to accelerating the mass ofcomponents in the transmission may not be observed. The higher torquecommand is based on the torque to accelerate the components of thetransmission to the desired speed of the transmission components afterthe shift, which is the transmission output speed before the shiftmultiplied by the on-coming gear ratio. In this way, wheel speed mayremain substantially constant while the transmission is shifted and theengine is stopped. The beginning of the transmission of the torque toaccelerate the transmission components may occur before the actual gearshift to time align the electric machine torque adjustment with theactual shift timing, thereby compensating for data transmission delays.Method 1500 proceeds to 1535.

At 1535, method 1500 commands the gear shift according to the gear shiftschedule. Actuators in the transmission move shift forks to engagesynchronizers to the on-coming gear in response to the gear shiftcommand. The transmission clutches are open while the vehicle is inelectric only propulsion mode so that the electric machine does notwaste energy rotating the engine. Method 1500 proceeds to 1540.

At 1540, method 1500 adjusts torque of the electric machine downstreamof the transmission (e.g., 125 of FIG. 3) in response to the torque toaccelerate the transmission components to a desired speed after theon-coming gear is engaged. Further, the electric machine torque isadjusted responsive to the driver demanded wheel torque. Thus, electricmachine torque=driver demand wheel torque times an axle ratio (ifpresent)+the torque to accelerate or decelerate transmission components,the transmission components being accelerated are related to the shift.The torque of the electric machine is adjusted at the same time orsimultaneously with the gear shift. Method 1500 proceeds to exit afteradjusting electric machine torque.

Referring now to FIG. 16A, a first block diagram for determining anamount of torque to accelerate transmission components related to a gearshift while the vehicle is in an electric only propulsion mode is shown.The method of block diagram 1600 may be used in the method of FIG. 15.

Transmission controller (e.g., 354 of FIG. 3) outputs an estimatedtorque to accelerate the transmission components (e.g., synchronizers,gears, layshafts, output side of a clutch, etc.) to multiplier block1608. For example, if an upshift from third gear to fourth gear oftransmission 125 shown in FIG. 4 is scheduled, the speed of on-cominggear is fourth gear (e.g., 426) is changed along with the speed ofsynchronizer 484, speed of layshaft 442, speed of input shaft 404, andspeed of input side of clutch 127 shown in FIG. 4. In one example, theestimated torque to accelerate the transmission components may be theinertia of the components times the angular acceleration from theoriginal speed of the transmission components to the desired speed ofthe transmission components after the on-coming gear is engaged. Thegear ratio between the electric machine and the transmission componentsbeing accelerated or decelerated is input at block 1604, which ismultiplied by the torque to accelerate the transmission components atblock 1608 to provide a compensation torque. The compensation torque isoutput from block 1608 to summing junction 1610 where it is added to thedriver demand torque. The output of summing junction 1610 is provided tothe electric machine controller 352 as a torque request of the electricmachine.

Referring now to FIG. 16B, a second block diagram for determining anamount of torque to accelerate transmission components related to a gearshift while the vehicle is in an electric only propulsion mode is shown.The method of block diagram 1620 may be used in the method of FIG. 15.

Transmission input shaft speed is input at block 1622. A previous valueof transmission input shaft speed is stored to memory at block 1604. Theprevious transmission input shaft speed output from block 1624 issubtracted from the present transmission input shaft speed output fromblock 1622 at summing junction 1630. The output of summing junction 1630is input into low pass filter 1632. The output of low pass filter 1632is input to block 1634 where it is divided by a sample time 1628 of aninput shaft speed sensor, which provides the input shaft speed to block1622. The output of block 1634 is multiplied by the inertia oftransmission components being accelerated due to the gear shift 1626 atblock 1636. The output of block 1636 is multiplied by a gear ratiobetween the electric machine and the transmission components beingaccelerated due to the gear shift 1637 at block 1638. The output ofblock 1638 is a compensation torque for shifting the transmission toavoid driveline torque disturbances and vehicle speed disturbances. Theoutput of block 1638 is added to the driver demand torque 1642 atsumming junction 1640. The output of summing junction 1640 is providedto the electric machine controller 352 as a torque request of theelectric machine.

Referring now to FIG. 16C, a third block diagram for determining anamount of torque to accelerate transmission components related to a gearshift while the vehicle is in an electric only propulsion mode is shown.The method of block diagram 1650 may be used in the method of FIG. 15.

Transmission output shaft speed is input at block 1652. A previous valueof transmission output shaft speed is stored to memory at block 1653.The previous transmission input shaft speed output from block 1653 issubtracted from the present transmission input shaft speed output fromblock 1652 at summing junction 1655. The output of summing junction 1655is input to block 1656 where it is divided by a sample time 1657 of aninput shaft speed sensor, which provides the output shaft speed to block1652. The output of block 1656 is multiplied by a ratio of a previouslylocked gear ratio (e.g., off-going gear) at block 1658. The output ofblock 1658 is subtracted from the output of block 1662 at summingjunction 1664.

Transmission input shaft speed is input at block 1659. A previous valueof transmission input shaft speed is stored to memory at block 1660. Theprevious transmission input shaft speed output from block 1660 issubtracted from the present transmission input shaft speed output fromblock 1659 at summing junction 1661. The output of summing junction 1661is divided by a sample time 1663 of an input shaft speed sensor, whichprovides the input shaft speed to block 1659. The output of block 1662is input to summing junction 1664.

The output of summing junction 1664 is input into low pass filter 1665.The output of low pass filter 1665 is input to block 1666 where itmultiplied by the inertia of transmission components being accelerateddue to the gear shift 1667. The output of block 1666 is multiplied by agear ratio between the electric machine and the transmission componentsbeing accelerated due to the gear shift 1680 at block 1668. The outputof block 1668 is a compensation torque for shifting the transmission toavoid driveline torque disturbances and vehicle speed disturbances. Theoutput of block 1668 is added to the driver demand torque 1671 atsumming junction 1669. The output of summing junction 1669 is providedto the electric machine controller 352 as a torque request of theelectric machine.

Referring now to FIG. 16D, a fourth block diagram for determining anamount of torque to accelerate transmission components related to a gearshift while the vehicle is in an electric only propulsion mode is shown.The method of block diagram 1675 may be used in the method of FIG. 15.

Block 1680 provides a switch like function to select from predeterminedvalues of positive torque compensation 1678, negative torquecompensation 1679, and no torque compensation 1677 (e.g., zero) based ona determination as to whether shifting gears accelerates components ofthe transmission or decelerates components of the transmission. Thedetermination may be based on whether the shift is an upshift or adownshift. The determination is input to switch 1680 at 1676 and thedetermination causes block 1680 to output one of 1678, 1679, and 1677 tosumming junction 1682. The output of block 1680 is added to the driverdemand torque 1685 at summing junction 1682. The output of summingjunction 1682 is provided to the electric machine controller 352 as atorque request of the electric machine.

Referring now to FIG. 17A, a simulated gear shift without compensatingthe torque of electric machine positioned downstream of the transmissionis shown. The sequence may be provided via the system of FIGS. 1A-4 whentorque compensation is not provided while shifting the transmission withthe engine is stopped and not combusting air and fuel.

The first plot from the top of FIG. 17A is a plot of transmission inputshaft speed versus time. The vertical axis represents transmission inputshaft speed and transmission input shaft speed increases in thedirection of the vertical axis arrow. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure. Trace 1705 represents speed of a transmission inputshaft that engages with odd gears (e.g., 1^(st) gear, 3^(rd) gear, and5^(th) gear) (e.g., 402 of FIG. 4). Trace 1710 represents speed of atransmission input shaft that engages with even gears (e.g., 2^(nd)gear, 4^(th) gear, and 6^(th) gear) (e.g., 404 of FIG. 4).

The second plot from the top of FIG. 17A is a plot of electric machinetorque versus time. The vertical axis represents electric machine torqueand electric machine torque increases in the direction of the verticalaxis arrow. The horizontal axis represents time and time increases fromthe left side of the figure to the right side of the figure.

The third plot from the top of FIG. 17A is a plot of vehicle speedversus time. The vertical axis represents vehicle speed and vehiclespeed increases in the direction of the vertical axis arrow. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

At time T40, the transmission input shaft speeds are at a lower leveland electric machine torque is at a middle level. Vehicle speed isconstant and non-zero. Engine rotational speed is zero and the engine isnot combusting air and fuel (not shown).

At time T41, a gear shift is initiated so that transmission input speedis at a desired speed in preparation for an engine start. As theon-coming gear is engaged, the transmission input shaft speed increasesresponsive to torque provided through the transmission output shaft viathe electric machine positioned downstream of the transmission (e.g.,125). The torque of the electric machine is constant since the electricmachine is providing the driver demand torque and the driver demandtorque has not changed (not shown). However, the vehicle speed isreduced as the transmission input shafts accelerate. The dip in vehiclespeed is caused by the net torque delivered to the vehicle wheelsdecreasing as a portion of the electric machine torque accelerates thetransmission's internal components to a new speed that is a function ofthe present vehicle speed and the engaged transmission gear.

At time T42, the input shafts reach a final speed after the componentsof the transmission reach a new speed that is a function of vehiclespeed and the selected gear ratio. The vehicle speed returns to near itsoriginal value before the gear shift and the electric machine torqueremains constant.

Thus, without compensating electric machine torque that acceleratestransmission components, vehicle speed changes in a way that may not bedesired. As such, electric machine torque compensation may be desirable.

Referring now to FIG. 17B, a simulated gear shift with compensating thetorque of electric machine positioned downstream of the transmission isshown. The sequence may be provided via the system of FIGS. 1A-4 and themethod of FIG. 15 when torque compensation is provided for shifting thetransmission with the engine is stopped and not combusting air and fuel.

The first plot from the top of FIG. 17B is a plot of transmission inputshaft speed versus time. The vertical axis represents transmission inputshaft speed and transmission input shaft speed increases in thedirection of the vertical axis arrow. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure. Trace 1755 represents speed of a transmission inputshaft that engages with odd gears (e.g., 1^(st) gear, 3^(rd) gear, and5^(th) gear) (e.g., 402). Trace 1760 represents speed of a transmissioninput shaft that engages with even gears (e.g., 2^(nd) gear, 4^(th)gear, and 6^(th) gear) (e.g., 404).

The second plot from the top of FIG. 17B is a plot of electric machinetorque versus time. The vertical axis represents electric machine torqueand electric machine torque increases in the direction of the verticalaxis arrow. The horizontal axis represents time and time increases fromthe left side of the figure to the right side of the figure.

The third plot from the top of FIG. 17B is a plot of vehicle speedversus time. The vertical axis represents vehicle speed and vehiclespeed increases in the direction of the vertical axis arrow. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

At time T45, the transmission input shaft speeds are at a lower leveland electric machine torque is at a middle level. Vehicle speed isconstant and non-zero. Engine rotational speed is zero and the engine isnot combusting air and fuel (not shown).

At time T46, a gear shift is initiated so that transmission input speedis at a desired speed in preparation for an engine start. As theon-coming gear is engaged, the transmission input shaft speed increasesresponsive to torque provided through the transmission output shaft viathe electric machine (e.g., 120) positioned downstream of thetransmission. The torque of the electric machine is increased tocompensate for accelerating components of the transmission related tothe gear shift. The electric machine torque is equal to demanded wheeltorque plus the compensation torque to accelerate transmissioncomponents responsive to the transmission gear shift. There is a smallchange in vehicle speed, but it is significantly less than if nocompensation torque is provided.

At time T47, the input shafts reach a final speed after the componentsof the transmission reach a new speed that is a function of vehiclespeed and the selected gear ratio. The compensation torque is zero atthis time so electric machine torque is a same torque as before the gearshift.

Thus, providing compensating torque via the electric machine to thedriveline may smooth vehicle speed and improve vehicle drivability. Thecompensation torque may be a predetermined value stored in controllermemory or it may be based on present vehicle conditions as describedherein.

Referring now to FIGS. 18A and 18B, a method for starting an engine thathas stopped rotating in a hybrid driveline is shown. The engine may bestarted while the vehicle in which the engine resides is moving orstationary. The method of FIGS. 18A and 18B may be incorporated into thesystem of FIGS. 1A-4 as executable instructions stored in non-transitorymemory of one or more controllers. Additionally, portions of the methodof FIGS. 18A and 18 b may be actions performed via the controllers shownin FIGS. 1A-4 to transform a state of a device or actuator in the realworld. The method shown in FIGS. 18A and 18B may operate in conjunctionand cooperation with other methods described herein. The method of FIGS.18A and 18B may be applied whether first clutch 126 or second clutch 127is being applied after an engine start.

At 1805, method 1800 determines vehicle operating conditions. Vehicleoperating conditions may include but are not limited to engine speed,vehicle speed, driver demanded or desired wheel torque, and torque ofthe electric machine (e.g., 120) positioned downstream of thetransmission. Method 1800 proceeds to 1810.

At 1810, method 1800 judges if the hybrid driveline is operating in anelectric only propulsion mode or electric vehicle mode. Method 1800 mayjudge that the hybrid driveline is operating in an electric onlypropulsion mode if the engine is stopped rotating and an electricmachine positioned in the driveline is providing torque to propel orslow the vehicle. The engine is not combusting air and fuel in electriconly mode. If method 1800 judges that the hybrid driveline is operatingin an electric only propulsion mode, the answer is yes and method 1800proceeds to 1820. Otherwise, the answer is no and method 1800 proceedsto 1815.

At 1815, method 1800 provides a desired wheel torque via engine torqueor engine torque and electric machine torque. In one example, a portionof the desired or requested wheel torque is provided by allocating afirst portion of the desired wheel torque to the engine and a secondportion of the desired wheel torque to the electric machine positioneddownstream of the transmission. Method 1800 proceeds to exit afterproviding the desired wheel torque.

At 1820, method 1800 judges if there is an increasing wheel torquerequest. In one example, method 1800 may judge that there is anincreasing wheel torque request if a current sample value of the desiredwheel torque is greater than a value of a most recent past sample of thedesired wheel torque. If method 1800 judges that there is an increasingwheel torque request, the answer is yes and method 1800 proceeds to1825. Otherwise, the answer is no and method 1800 proceeds to 1825.

At 1825, method 1800 increases torque of the electric machine downstreamof the transmission (e.g., 125) in response to the increasing requestedwheel torque. In particular, the electric machine torque may beincreased to match the desired wheel torque multiplied by any gear ratiobetween the electric machine and the wheels and accounting for the wheelrolling radius. Method 1800 proceeds to 1830.

At 1830, method 1800 engages a desired gear ratio and prepositions aclutch that selectively transmits torque to the desired gear ratio. Inone example, the desired gear ratio is based on vehicle speed anddesired wheel torque. The desired gear ratio may be extracted from atransmission shift schedule stored in memory. The transmission shiftschedule is indexed via vehicle speed and desired wheel torque. Thetransmission shift schedule outputs a gear ratio or desired gear. Theclutch that selectively provides torque to the desired gear ratio isprepositioned via a stroking pressure of fluid delivered to the clutch.The stroking pressure may be a pressure that moves clutch plates to aposition just before the clutch transfers torque from an input side ofthe clutch to an output side of the clutch. Method 1800 proceeds to1835.

At 1835, method 1800 starts the engine if the engine is not started.After the engine is started, or if the engine is combusting air andfuel, the engine speed is adjusted to a desired transmission input shaftspeed. The engine speed is accelerated to a speed greater than an engineidle speed. This engine speed may be referred to as an engine launchspeed. Increasing engine speed increases the engine's capacity toprovide larger torque amounts. If the vehicle in which the engine isoperating is moving, engine speed is increased to a desired transmissioninputs shaft speed plus a variable offset value. The engine is operatedin a speed control mode where engine torque is varied so that enginespeed follows a desired engine speed. Method 1800 proceeds to 1840.

At 1840, method 1800 judges if torque of the electric machine positionedin the driveline downstream of the transmission is greater than athreshold value. Method 1800 may estimate the electric machine torquevia current entering or exiting the electric machine. If method 1800judges that electric machine torque is greater than the threshold, theanswer is yes and method 1800 proceeds to 1845. Otherwise, the answer isno and method 1800 returns to 1820.

At 1845, method 1800 adjusts engine speed and torque capacity of theclutch that selectively transfers torque to the engaged transmissiongear responsive to desired wheel torque or a driver demanded wheeltorque. A driver or controller may request wheel torque via anaccelerator pedal or a controller variable. For example, if the desiredwheel torque continues increasing, the desired engine speed may beincreased to increase the engine's torque capacity. Additionally, thetorque capacity of the clutch that selectively transfers torque to theengaged gear may be increased as the desired wheel torque increases.Torque capacity of the clutch is increased by increasing pressure offluid supplied to the clutch. Similarly, if the desired wheel torquedecreases, the desired engine speed may be decreased to decrease theengine's torque capacity and the torque capacity of the clutch thatselectively transfers torque to the engaged gear may be decreased.Method 1800 proceeds to 1850.

At 1850, method 1800 judges if speed of the transmission input shaftthat transfers torque to the engaged gear plus an offset speed isgreater than engine launch speed. If method 1800 judges that speed ofthe transmission input shaft that transfers torque to the engaged gearplus an offset speed is greater than engine launch speed, the answer isyes and method 1800 proceeds to 1855. Otherwise, the answer is no andmethod 1800 returns to 1845.

At 1855 of FIG. 18B, the engine continues operating in speed controlmode and engine speed is commanded to follow speed of the transmissioninput shaft that transfers torque to the engaged gear plus an offsetspeed. In addition, the torque capacity of the clutch continues to becontrolled as a function of the desired wheel torque. Method 1800proceeds to 1860.

At 1860, method 1800 judges if engine crankshaft acceleration andacceleration of the transmission input shaft that selectively transferstorque to the engaged gear are substantially equal (e.g., within +10percent of each other) and if speed of the transmission input shaft thattransfers torque to the engaged gear is greater than engine launchspeed. If so, the answer is yes and method 1800 proceeds to 1865.Otherwise, the answer is no and method 1800 returns to 1855.

At 1865, method 1800 reduces the offset speed between the desired enginespeed and the desired speed of the transmission input shaft thatselectively transfers torque to the engaged gear. By reducing the offsetspeed, the engine speed and the speed of the transmission input shaftthat selectively transfers torque to the engaged gear may be broughttogether. Method 1800 proceeds to 1870.

At 1870, method 1800 judges if engine crankshaft speed and speed of thetransmission input shaft that selectively transfers torque to theengaged gear are substantially equal (e.g., within ±75 RPM of eachother). If so, the answer is yes and method 1800 proceeds to 1875.Otherwise, the answer is no and method 1800 returns to 1865.

At 1875, method 1800 locks the clutch that selectively transfers torqueto the engaged gear. The clutch may be locked via increasing pressure offluid supplied to the clutch. Method 1800 proceeds to 1880.

At 1880, method 1800 increases engine torque to provide the requestedwheel torque. Engine torque may be increased via opening a throttle ofthe engine, adjusting engine spark timing, or adjusting other enginetorque actuators. Method 1800 proceeds to exit.

In this way, an engine may be started and engine torque may be deliveredto the driveline of a hybrid vehicle so that the possibility ofdriveline torque disturbances may be reduced. Further, the method ofFIGS. 18A and 18B may be applied if the vehicle in which the engineoperates is stationary or moving.

Turning now to FIG. 19A, an example prophetic timeline 1900 is shown foran engine connection algorithm, according to method 1800 depicted inFIGS. 18A-18B, and as applied to the systems described herein and withreference to FIGS. 1A-4. The upper graph depicts rotational speed of anengine (e.g. 110) and transmission input shaft (e.g. 402, 404) on thevertical-axis, while the lower graph depicts torque profiles (wheeltorque, engine torque, total engine crankshaft torque). Thehorizontal-axis of both the upper and lower graphs depict time. Morespecifically, timeline 1900 includes plot 1905, indicating a desiredengine speed, and plot 1910, indicating engine speed, over time.Timeline 1900 further includes plot 1915, indicating input shaft speed,and plot 1920, indicating input shaft speed plus an offset, over time.Timeline 1900 further includes plot 1923, indicating a normal enginestarting speed profile (e.g., an engine speed profile for when theengine is started while the vehicle's transmission is in park and not inresponse to an increasing torque demand), over time. Timeline 1900further includes plot 1925, indicating a desired total wheel torque, andplot 1930, indicating an actual wheel torque from an electric machine(e.g. 120), over time. Timeline 1900 further includes plot 1935,indicating a wheel torque from a launch clutch through the vehicletransmission and final drive, over time. Timeline 1900 further includesplot 1940, indicating total engine crankshaft torque multiplied by atransmission and final drive ratio, over time. Arrows 1942 indicatingengine torque needed to accelerated engine inertia.

Furthermore, arrow 1945 indicates a period of time between time T50 andT52 wherein the launch clutch (e.g., clutch that is closed to acceleratethe vehicle) is open, two-way arrow 1950 indicates a period of timebetween time T52 and T55 wherein the launch clutch is slipping, andarrow 1955 indicates a period of time between time T55 and T56, whereinthe launch clutch is locked, over time.

At time T50, the engine is on and is rotating at normal idle speed,indicated by plot 1910. Furthermore, the vehicle is stationary, astorque is not being transmitted to the wheels, indicated by the absenceof an indication of torque at time T50. While this example timelineillustrates an example condition wherein the engine is on at an idlespeed, it may be understood that the description contained herein withregard to the engine connection algorithm may be conducted if the engineis initially off, without departing from the scope of this disclosure.

At time T51, and accelerator tip-in imposes an increasing wheel torquerequest. As such, between time T51 and T52, the vehicle is propelled viathe electric machine with the engine and dual clutch transmission (e.g.125) preparing to transmit engine torque to the wheels. Thus, betweentime T51 and T52, desired wheel torque increases along a rate limitedtrajectory up to a value determined by the accelerator pedal position(and potentially other signals). Such a rate may be determined bystability limits, drivetrain twist management, calibration values, orother values calculated to provide desired vehicle response.

Accordingly, between time T51 and T52, electric machine wheel torque,indicated by plot 1930, increases to follow the desired torque referencewith electrical propulsion only. Leading with electric drive may providefast vehicle response, may give a time buffer to prepare the engine andDCT to transmit torque, and may allow the electric machine to be used toreduce wheel torque quickly for traction control, stability control, ora change of mind accelerator pedal lift if needed.

Further, during time T51 and T52, the DCT may prepare the target inputclutch to carry capacity and lock the desired target gear ratio. Forexample, a clutch actuator (e.g. 489 of FIG. 4) may be filled withpressurized fluid. As an example, in a case where the vehicle isstationary, the desired gear ratio may be first gear (e.g. 420). In acase where the vehicle is moving at the time of the tip-in (e.g.,increase in accelerator pedal position), the desired gear may bedetermined based on an engine torque multiplication needed to meet thewheel torque demand and the desired engine speed at the time ofconnection of the engine.

If the engine is running in idle speed control, as in example timeline1900, the desired engine speed may rise. In a case where the vehicle isstationary, as in example timeline 1900, the desired speed may riseabove idle to a value for vehicle launch to provide the engine moretorque capacity for better engine speed regulation with load from thelaunch clutch, and also to give an indication to the driver that thevehicle is responding to the tip-in request. In an example where thevehicle is moving, the desired engine speed may be a desired DCT inputshaft speed plus variable offset speed. Still further, in a case wherethe engine is off, it may be started and put into speed control with thesame desired engine speed as discussed above.

At time T52, it may be understood that electric machine (e.g., 120)torque is above a configurable threshold, indicating that it is close torunning out of capability and it may be further understood that enginespeed is above desired transmission input shaft speed.

Accordingly, between time T52 and T53, it may be understood thatelectric machine torque is making torque above an electric machinetorque threshold (not shown), indicating that it is close to running outof capacity to meet driver demand. Thus, engine torque may be added tothe wheels to achieve the required wheel torque profile. Adding enginetorque to the wheels to achieve the required torque profile may includeengine speed greater than desired transmission input shaft speed totransmit positive torque through a slipping clutch. In an examplecondition where the vehicle is stationary, the positive torque may betransmitted through the slipping clutch without delay, due to the inputshaft speed being low. However, in an example condition where thevehicle is moving, there may be a time delay while engine speed risesabove the desired input shaft speed before the clutch can be applied totransmit positive torque to the driveline. In either case, clutch torquemay be ramped in at the same rate the motor torque was applied tomaintain constant driveline twist and vehicle acceleration.

In an example condition where the vehicle is stationary, vehicle speedwill be low, and the input shaft of the transmission used for thevehicle launch gear may be below a minimum engine speed that can be usedfor launch, so the input clutch may slip to transmit engine torque tothe wheels. Because constant engine speed is desired during such a time,engine torque may be approximately equal to the increasing clutchtorque. Driver demand may dictate the peak slipping clutch torquebecause the clutch is the device controlling wheel torque and vehicleacceleration at this time. Accordingly, accelerator input and driverdemand may be mapped to clutch torque while the clutch is slipping. Inother words, clutch torque capacity may be a function of driver demandtorque.

In an example condition where the vehicle was initially moving, enginespeed may be above the desired input shaft speed, and further the inputshaft speed may be above a minimum engine launch speed, thus enablingtransmission of positive torque within minimal clutch slipping.

Furthermore, responsive to the driver reducing desired wheel torque, acombination of reducing electric machine torque and slipping clutchtorque capacity may be conducted to meet the wheel torque reduction. Atthis point, the DCT clutches may be opened to return the vehicle toelectric propulsion mode, or the vehicle may continue to accelerate withthe launch clutch slipping until the transmission input shaft speed ishigh enough for the clutch to lock at the engine launch speed for hybridvehicle propulsion.

At time T53, target input shaft speed plus offset rises above the launchengine speed. Accordingly, between time T53 and T54, the engine speedcontroller may increase engine torque to follow input shaft speed plusan additional offset. The additional offset may be used to keep positiveslip across the clutch and prevent it from locking before desired. Itmay be understood that the slipping clutch is in control of wheeltorque, thus there is no change in vehicle operation. Accordingly, thetime period between time T53 and T54 may be utilized to matchacceleration between the input shaft and crankshaft to achieve a smoothclutch lock event by reducing an amount of engine torque increase at thepoint of locking to maintain the same vehicle acceleration withincreased driveline inertia at the time of lock.

At time T54, crankshaft and transmission input have the sameacceleration and input speed is above launch speed. Thus, between timeT55 and T56, once the acceleration of the engine crankshaft and inputshaft are the same and the input shaft is above the minimum engine speedfor the clutch to lock, offset between the engine speed control targetand input shaft speed is reduced to zero. This may be linearly reducedas a function of time, or it may be shaped using some other means suchthat the engine speed controller may reduce engine torque to bring thetwo shaft speeds together, to allow the clutch to lock. By having theengine speed controller control clutch locking instead of coordinatingengine and clutch torque may automatically compensate for engine andclutch torque errors, and may provide robust locking times determined bya rate at which the speed offset is reduced.

At time T55, engine and input shaft speeds are matched and clutchlocking is achieved. Thus, between time T55 and T56, once the engine andinput shaft speeds are matched within a threshold, DCT target inputclutch capacity may be rapidly increased to lock the clutch withoutaffecting drivetrain wheel torque, as the speeds and accelerations maybe closely matched. When the clutch locks, torque transmitted throughthe clutch into the transmission may change from its slipping capacityto engine torque minus the torque needed to accelerate the engineinertia. The more closely matched the acceleration of the engine andinput shafts when their speeds match, the less difference there will bein torque as a result of the lock. The acceleration of the engine may beat least somewhat lower than acceleration of the input shaft for thespeeds to intersect and enable clutch locking. Accordingly, some amountof engine torque may be quickly added to the transmission to compensatefor extra inertia added to the input clutch by the engine. After thelock, engine torque transmitted to the wheels through the transmissionmay be controlled directly by the engine torque controller, and not theclutch. To maintain a same rate of torque into the transmission, theengine may need to produce the desired wheel torque contribution fromthe engine plus the torque to continue the same rate of acceleration ofthe engine inertia.

Thus, transition to hybrid propulsion may be completed between time T55and T56, and the electric machine torque may be blended out and enginetorque increased according to energy management to achieve a desiredtorque split between the two the electric machine and engine.

Turning now to FIG. 19B, an example prophetic timeline 1900 is shown foran engine connection algorithm, according to method 1800 depicted inFIGS. 18A-18B, and as applied to the systems described herein and withreference to FIGS. 1A-4. In this example, the engine is started whilethe vehicle in which the engine is rolling on a road. The upper graphdepicts rotational speed of an engine (e.g. 110) and transmission inputshaft (e.g. 402, 404) on the vertical-axis, while the lower graphdepicts torque profiles (wheel torque, engine torque, total enginecrankshaft torque). The horizontal-axis of both the upper and lowergraphs depict time. More specifically, timeline 1950 includes plot 1905,indicating a desired engine speed, and plot 1910, indicating enginespeed, over time. Timeline 1950 further includes plot 1915, indicatinginput shaft speed, and plot 1920, indicating input shaft speed plus anoffset, over time. Timeline 1950 further includes plot 1925, indicatinga desired total wheel torque, and plot 1930, indicating an actual wheeltorque from an electric machine (e.g. 120), over time. Timeline 1950further includes plot 1935, indicating a wheel torque from a launchclutch through the vehicle transmission and final drive, over time.Timeline 1900 further includes plot 1940, indicating total enginecrankshaft torque multiplied by a transmission and final drive ratio,over time. Arrows 1942 indicating engine torque needed to acceleratedengine inertia.

Furthermore, arrow 1945 indicates a period of time between time T60 andT62 wherein the launch clutch (e.g., clutch that is closed to acceleratethe vehicle) is open, two-way arrow 1950 indicates a period of timebetween time T62 and T65 wherein the launch clutch is slipping, andarrow 1955 indicates a period of time between time T65 and T66, whereinthe launch clutch is locked, over time.

At time T60, the engine is stopped, not rotating, and not combusting airand fuel as indicated by plot 1910. Furthermore, the vehicle is rollingvia power from the electric machine (e.g., 120) as indicated by actualwheel torque from the electric machine 1930 at time T50.

At time T61, and accelerator tip-in imposes an increasing wheel torquerequest. As such, between time T61 and T62, the vehicle is propelled viathe electric machine with the engine and dual clutch transmission (e.g.125) preparing to transmit engine torque to the wheels. Thus, betweentime T61 and T62, desired wheel torque 1925 increases along a ratelimited trajectory up to a value determined by the accelerator pedalposition (and potentially other signals). Such a rate may be determinedby stability limits, drivetrain twist management, calibration values, orother values calculated to provide desired vehicle response.

At time T61, desired engine speed 1905 increases to indicate a requestto start the engine. The engine is started and it begins to accelerateto the input shaft speed of the input shaft that is coupled to thepresently engaged transmission gear plus an offset speed value 1920. Theengine is accelerated to its desired speed in a speed control mode.

Accordingly, between time T61 and T62, electric machine wheel torque,indicated by plot 1930, increases to follow the desired torque referencewith electrical propulsion only. Leading with electric drive may providefast vehicle response, may give a time buffer to prepare the engine andDCT to transmit torque, and may allow the electric machine to be used toreduce wheel torque quickly for traction control, stability control, ora change of mind accelerator pedal lift if needed.

Further, during time T61 and T62, the DCT may prepare the target inputclutch to carry capacity and lock the desired target gear ratio. Forexample, a clutch actuator (e.g. 489 of FIG. 4) may be filled withpressurized fluid. As an example, in a case where the vehicle isstationary, the desired gear ratio may be first gear (e.g. 420). In acase where the vehicle is moving at the time of the tip-in (e.g.,increase in accelerator pedal position), the desired gear may bedetermined based on an engine torque multiplication needed to meet thewheel torque demand and the desired engine speed at the time ofconnection of the engine.

At time T62, it may be understood that electric machine (e.g., 120)torque is above a configurable threshold, indicating that it is close torunning out of capability and it may be further understood that enginespeed is above desired transmission input shaft speed.

Accordingly, between time T62 and T63, it may be understood thatelectric machine torque is making torque above an electric machinetorque threshold (not shown), indicating that it is close to running outof capacity to meet driver demand. Thus, engine torque may be added tothe wheels to achieve the required wheel torque profile.

Because constant engine speed is desired during such a time, enginetorque may be approximately equal to the increasing clutch torque.Driver demand may dictate the peak slipping clutch torque because theclutch is the device controlling wheel torque and vehicle accelerationat this time. Accordingly, accelerator input and driver demand may bemapped to clutch torque while the clutch is slipping. In other words,clutch torque capacity may be a function of driver demand torque.

At time T63, desired input shaft speed plus offset rises above thelaunch engine speed. Accordingly, between time T63 and T64, the enginespeed controller may increase engine torque to follow input shaft speedplus an additional offset. The additional offset may be used to keeppositive slip across the clutch and prevent it from locking beforedesired. The time period between time T63 and T64 may be utilized tomatch acceleration between the input shaft and crankshaft to achieve asmooth clutch lock event by reducing an amount of engine torque increaseat the point of locking to maintain the same vehicle acceleration withincreased driveline inertia at the time of lock.

At time T64, crankshaft and transmission input have the sameacceleration and input speed is above launch speed. Thus, between timeT65 and T66, once the acceleration of the engine crankshaft and inputshaft are the same and the input shaft is above the minimum engine speedfor the clutch to lock, offset between the engine speed control targetand input shaft speed is reduced to zero.

At time T65, engine and input shaft speeds are matched and clutchlocking is achieved. Thus, between time T65 and T66, once the engine andinput shaft speeds are matched within a threshold, DCT target inputclutch capacity may be rapidly increased to lock the clutch withoutaffecting drivetrain wheel torque, as the speeds and accelerations maybe closely matched. Thus, transition to hybrid propulsion may becompleted between time T65 and T66. The engine may be started from astopped state and accelerated to a speed of a transmission input shaft.One of the transmission clutches may be closed with clutch slipresponsive to driver demand torque. The closing clutch transfers enginetorque to the vehicle wheels to meet the driver demand torque. Theclosing clutch is fully closed after the engine speed and thetransmission speed are substantially equal.

In this way, a hybrid vehicle may be enabled to launch the vehicle in anelectric-only mode of operation, or silent drive, without activating theengine in a fueled mode of operation and then deactivating the engine,simply to release the park pawl. Instead, the park pawl may be releasedwithout fueled engine operation, which may increase vehicle operatorsatisfaction and which may improve fuel economy.

The technical effect is to recognize that by spinning the engineunfueled, and/or by operating an electric transmission pump, the parkpawl may be released without fueled engine operation. Such operationsmay enable an increase in fuel efficiency for hybrid vehicles.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware.

Further, portions of the methods may be physical actions taken in thereal world to change a state of a device. The specific routinesdescribed herein may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various actions, operations,and/or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example examples described herein, but is provided forease of illustration and description. One or more of the illustratedactions, operations and/or functions may be repeatedly performeddepending on the particular strategy being used. Further, the describedactions, operations and/or functions may graphically represent code tobe programmed into non-transitory memory of the computer readablestorage medium in the engine control system, where the described actionsare carried out by executing the instructions in a system including thevarious engine hardware components in combination with the electroniccontroller. One or more of the method steps described herein may beomitted if desired.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific examples are notto be considered in a limiting sense, because numerous variations arepossible. For example, the above technology can be applied to V-6, I-4,I-6, V-12, opposed 4, and other engine types. The subject matter of thepresent disclosure includes all novel and non-obvious combinations andsub-combinations of the various systems and configurations, and otherfeatures, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A driveline operating method, comprising:engaging a parking pawl to an output shaft of a dual clutch transmissionin response to a request to enter a vehicle into a parked state; anddisengaging the parking pawl via rotating an engine via an integratedstarter/generator in response to a request to propel the vehicle solelyvia power of an electric machine positioned downstream of the dualclutch transmission.
 2. The method of claim 1, further comprisingreducing pumping work of the engine in response to the request to propelthe vehicle solely via power of the electric machine.
 3. The method ofclaim 1, where the integrated starter/generator is coupled to theengine.
 4. The method of claim 1, where the engine is not combusting airand fuel while the parking pawl is engaged.
 5. The method of claim 1,further comprising rotating a pump via rotating the engine.
 6. Themethod of claim 5, further comprising supplying fluid via the pump torelease the parking pawl.
 7. The method of claim 1, ceasing enginerotation in response to an indication that the parking pawl is released.8. A driveline operating method, comprising: engaging a parking pawl toan output shaft of a dual clutch transmission in response to a requestto enter a vehicle into a parked state; and disengaging the parking pawlvia activating an electric pump in response to a request to propel thevehicle solely via power of an electric machine positioned downstream ofthe dual clutch transmission.
 9. The method of claim 8, furthercomprising deactivating the electric pump in response to an indicationthat the parking pawl is released.
 10. The method of claim 8, furtherproviding torque to vehicle wheels via the electric machine in responseto the parking pawl being released.
 11. The method of claim 8, furthercomprising starting an engine in response to an indication that theparking pawl is not released after commanding the parking pawl released.12. The method of claim 11, further comprising rotating a mechanicalpump via the engine and releasing the parking pawl after the indicationthat the parking pawl is not released.
 13. The method of claim 11,further comprising deactivating the electric pump in response to theindication that the parking pawl is not released.
 14. The method ofclaim 8, where the parking pawl is engaged via a spring.
 15. The methodof claim 8, where the dual clutch transmission is positioned in avehicle driveline between an engine and the electric machine.
 16. Asystem, comprising: an engine; a dual clutch transmission coupled to theengine, the dual clutch transmission including a parking pawl and ahydraulic pump in fluidic communication with the parking pawl; anelectric machine coupled to, and positioned downstream of, the dualclutch transmission; and a controller including executable instructionsstored in non-transitory memory to disengage the parking pawl viasupplying hydraulic fluid to the parking pawl via the hydraulic pump inresponse to a request to propel a vehicle via power supplied solely fromthe electric machine.
 17. The system of claim 16, where the hydraulicpump is electrically driven via an electric motor, the electric motornot coupled to the engine.
 18. The system of claim 17, furthercomprising additional instructions to rotate the hydraulic pump via theelectric motor in response to the request to propel the vehicle viapower supplied solely from the electric machine, and where the electricmachine is not the electric motor.
 19. The system of claim 16, furthercomprising additional instructions to rotate the hydraulic pump via theengine without starting the engine.
 20. The system of claim 16, wherethe parking pawl includes a spring for engaging the parking pawl.